aboutsummaryrefslogtreecommitdiffstats
path: root/activerecord/lib/active_record/associations.rb
blob: 56fe19a1dbdd33e93fbf8d96478ab4bba4e820f2 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
require 'active_record/associations/association_proxy'
require 'active_record/associations/association_collection'
require 'active_record/associations/belongs_to_association'
require 'active_record/associations/belongs_to_polymorphic_association'
require 'active_record/associations/has_one_association'
require 'active_record/associations/has_many_association'
require 'active_record/associations/has_many_through_association'
require 'active_record/associations/has_and_belongs_to_many_association'
require 'active_record/deprecated_associations'

module ActiveRecord
  class HasManyThroughAssociationNotFoundError < ActiveRecordError #:nodoc:
    def initialize(owner_class_name, reflection)
      super("Could not find the association #{reflection.options[:through].inspect} in model #{owner_class_name}")
    end
  end

  class HasManyThroughAssociationPolymorphicError < ActiveRecordError #:nodoc:
    def initialize(owner_class_name, reflection, source_reflection)
      super("Cannot have a has_many :through association '#{owner_class_name}##{reflection.name}' on the polymorphic object '#{source_reflection.class_name}##{source_reflection.name}'.")
    end
  end
  
  class HasManyThroughAssociationPointlessSourceTypeError < ActiveRecordError #:nodoc:
    def initialize(owner_class_name, reflection, source_reflection)
      super("Cannot have a has_many :through association '#{owner_class_name}##{reflection.name}' with a :source_type option if the '#{reflection.through_reflection.class_name}##{source_reflection.name}' is not polymorphic.  Try removing :source_type on your association.")
    end
  end
  
  class HasManyThroughSourceAssociationNotFoundError < ActiveRecordError #:nodoc:
    def initialize(reflection)
      through_reflection      = reflection.through_reflection
      source_reflection_names = reflection.source_reflection_names
      source_associations     = reflection.through_reflection.klass.reflect_on_all_associations.collect { |a| a.name.inspect }
      super("Could not find the source association(s) #{source_reflection_names.collect(&:inspect).to_sentence :connector => 'or'} in model #{through_reflection.klass}.  Try 'has_many #{reflection.name.inspect}, :through => #{through_reflection.name.inspect}, :source => <name>'.  Is it one of #{source_associations.to_sentence :connector => 'or'}?")
    end
  end

  class HasManyThroughSourceAssociationMacroError < ActiveRecordError #:nodoc:
    def initialize(reflection)
      through_reflection = reflection.through_reflection
      source_reflection  = reflection.source_reflection
      super("Invalid source reflection macro :#{source_reflection.macro}#{" :through" if source_reflection.options[:through]} for has_many #{reflection.name.inspect}, :through => #{through_reflection.name.inspect}.  Use :source to specify the source reflection.")
    end
  end

  class HasManyThroughCantAssociateNewRecords < ActiveRecordError #:nodoc:
    def initialize(owner, reflection)
      super("Cannot associate new records through '#{owner.class.name}##{reflection.name}' on '#{reflection.source_reflection.class_name rescue nil}##{reflection.source_reflection.name rescue nil}'. Both records must have an id in order to create the has_many :through record associating them.")
    end
  end

  class EagerLoadPolymorphicError < ActiveRecordError #:nodoc:
    def initialize(reflection)
      super("Can not eagerly load the polymorphic association #{reflection.name.inspect}")
    end
  end

  class ReadOnlyAssociation < ActiveRecordError #:nodoc:
    def initialize(reflection)
      super("Can not add to a has_many :through association.  Try adding to #{reflection.through_reflection.name.inspect}.")
    end
  end

  module Associations # :nodoc:
    def self.included(base)
      base.extend(ClassMethods)
    end

    # Clears out the association cache 
    def clear_association_cache #:nodoc:
      self.class.reflect_on_all_associations.to_a.each do |assoc|
        instance_variable_set "@#{assoc.name}", nil
      end unless self.new_record?
    end
    
    # Associations are a set of macro-like class methods for tying objects together through foreign keys. They express relationships like 
    # "Project has one Project Manager" or "Project belongs to a Portfolio". Each macro adds a number of methods to the class which are 
    # specialized according to the collection or association symbol and the options hash. It works much the same way as Ruby's own attr* 
    # methods. Example:
    #
    #   class Project < ActiveRecord::Base
    #     belongs_to              :portfolio
    #     has_one                 :project_manager 
    #     has_many                :milestones
    #     has_and_belongs_to_many :categories
    #   end
    #
    # The project class now has the following methods (and more) to ease the traversal and manipulation of its relationships:
    # * <tt>Project#portfolio, Project#portfolio=(portfolio), Project#portfolio.nil?</tt>
    # * <tt>Project#project_manager, Project#project_manager=(project_manager), Project#project_manager.nil?,</tt>
    # * <tt>Project#milestones.empty?, Project#milestones.size, Project#milestones, Project#milestones<<(milestone),</tt>
    #   <tt>Project#milestones.delete(milestone), Project#milestones.find(milestone_id), Project#milestones.find(:all, options),</tt>
    #   <tt>Project#milestones.build, Project#milestones.create</tt>
    # * <tt>Project#categories.empty?, Project#categories.size, Project#categories, Project#categories<<(category1),</tt>
    #   <tt>Project#categories.delete(category1)</tt>
    #
    # === A word of warning
    #
    # Don't create associations that have the same name as instance methods of ActiveRecord::Base. Since the association
    # adds a method with that name to its model, it will override the inherited method and break things.
    # For instance, #attributes and #connection would be bad choices for association names.
    #
    # == Example
    #
    # link:files/examples/associations.png
    #
    # == Cardinality and associations
    # 
    # ActiveRecord associations can be used to describe relations with one-to-one, one-to-many
    # and many-to-many cardinality. Each model uses an association to describe its role in
    # the relation. In each case, the belongs_to association is used in the model that has
    # the foreign key.
    #
    # === One-to-one
    #
    # Use has_one in the base, and belongs_to in the associated model.
    #
    #   class Employee < ActiveRecord::Base
    #     has_one :office
    #   end
    #   class Office < ActiveRecord::Base
    #     belongs_to :employee    # foreign key - employee_id
    #   end
    #
    # === One-to-many
    #
    # Use has_many in the base, and belongs_to in the associated model.
    #
    #   class Manager < ActiveRecord::Base
    #     has_many :employees
    #   end
    #   class Employee < ActiveRecord::Base
    #     belongs_to :manager     # foreign key - manager_id
    #   end
    #
    # === Many-to-many
    #
    # There are two ways to build a many-to-many relationship.
    #
    # The first way uses a has_many association with the :through option and a join model, so
    # there are two stages of associations.
    #
    #   class Assignment < ActiveRecord::Base
    #     belongs_to :programmer  # foreign key - programmer_id
    #     belongs_to :project     # foreign key - project_id
    #   end
    #   class Programmer < ActiveRecord::Base
    #     has_many :assignments
    #     has_many :projects, :through => :assignments
    #   end
    #   class Project < ActiveRecord::Base
    #     has_many :assignments
    #     has_many :programmers, :through => :assignments
    #   end
    #
    # For the second way, use has_and_belongs_to_many in both models. This requires a join table
    # that has no corresponding model or primary key.
    #
    #   class Programmer < ActiveRecord::Base
    #     has_and_belongs_to_many :projects       # foreign keys in the join table
    #   end
    #   class Project < ActiveRecord::Base
    #     has_and_belongs_to_many :programmers    # foreign keys in the join table
    #   end
    #
    # It is not always a simple decision which way of building a many-to-many relationship is best.
    # But if you need to work with the relationship model as its own entity, then you'll need to
    # use has_many :through. Use has_and_belongs_to_many when working with legacy schemas or when
    # you never work directly with the relationship itself.
    #
    # == Is it a belongs_to or has_one association?
    #
    # Both express a 1-1 relationship, the difference is mostly where to place the foreign key, which goes on the table for the class
    # saying belongs_to. Example:
    #
    #   class User < ActiveRecord::Base
    #     # I reference an account.
    #     belongs_to :account
    #   end
    #
    #   class Account < ActiveRecord::Base
    #     # One user references me.
    #     has_one :user
    #   end
    #
    # The tables for these classes could look something like:
    #
    #   CREATE TABLE users (
    #     id int(11) NOT NULL auto_increment,
    #     account_id int(11) default NULL,
    #     name varchar default NULL,
    #     PRIMARY KEY  (id)
    #   )
    #
    #   CREATE TABLE accounts (
    #     id int(11) NOT NULL auto_increment,
    #     name varchar default NULL,
    #     PRIMARY KEY  (id)
    #   )
    #
    # == Unsaved objects and associations
    #
    # You can manipulate objects and associations before they are saved to the database, but there is some special behaviour you should be
    # aware of, mostly involving the saving of associated objects.
    #
    # === One-to-one associations
    #
    # * Assigning an object to a has_one association automatically saves that object and the object being replaced (if there is one), in
    #   order to update their primary keys - except if the parent object is unsaved (new_record? == true).
    # * If either of these saves fail (due to one of the objects being invalid) the assignment statement returns false and the assignment
    #   is cancelled.
    # * If you wish to assign an object to a has_one association without saving it, use the #association.build method (documented below).
    # * Assigning an object to a belongs_to association does not save the object, since the foreign key field belongs on the parent. It does
    #   not save the parent either.
    #
    # === Collections
    #
    # * Adding an object to a collection (has_many or has_and_belongs_to_many) automatically saves that object, except if the parent object
    #   (the owner of the collection) is not yet stored in the database.
    # * If saving any of the objects being added to a collection (via #push or similar) fails, then #push returns false.
    # * You can add an object to a collection without automatically saving it by using the #collection.build method (documented below).
    # * All unsaved (new_record? == true) members of the collection are automatically saved when the parent is saved.
    #
    # === Association callbacks
    #
    # Similiar to the normal callbacks that hook into the lifecycle of an Active Record object, you can also define callbacks that get
    # trigged when you add an object to or removing an object from a association collection. Example:
    #
    #   class Project
    #     has_and_belongs_to_many :developers, :after_add => :evaluate_velocity
    #
    #     def evaluate_velocity(developer)
    #       ...
    #     end
    #   end 
    #
    # It's possible to stack callbacks by passing them as an array. Example:
    # 
    #   class Project
    #     has_and_belongs_to_many :developers, :after_add => [:evaluate_velocity, Proc.new { |p, d| p.shipping_date = Time.now}]
    #   end
    #
    # Possible callbacks are: before_add, after_add, before_remove and after_remove.
    #
    # Should any of the before_add callbacks throw an exception, the object does not get added to the collection. Same with
    # the before_remove callbacks, if an exception is thrown the object doesn't get removed.
    #
    # === Association extensions
    #
    # The proxy objects that controls the access to associations can be extended through anonymous modules. This is especially
    # beneficial for adding new finders, creators, and other factory-type methods that are only used as part of this association.
    # Example:
    #
    #   class Account < ActiveRecord::Base
    #     has_many :people do
    #       def find_or_create_by_name(name)
    #         first_name, last_name = name.split(" ", 2)
    #         find_or_create_by_first_name_and_last_name(first_name, last_name)
    #       end
    #     end
    #   end
    #
    #   person = Account.find(:first).people.find_or_create_by_name("David Heinemeier Hansson")
    #   person.first_name # => "David"
    #   person.last_name  # => "Heinemeier Hansson"
    #
    # If you need to share the same extensions between many associations, you can use a named extension module. Example:
    #
    #   module FindOrCreateByNameExtension
    #     def find_or_create_by_name(name)
    #       first_name, last_name = name.split(" ", 2)
    #       find_or_create_by_first_name_and_last_name(first_name, last_name)
    #     end
    #   end
    #
    #   class Account < ActiveRecord::Base
    #     has_many :people, :extend => FindOrCreateByNameExtension
    #   end
    #
    #   class Company < ActiveRecord::Base
    #     has_many :people, :extend => FindOrCreateByNameExtension
    #   end
    #
    # If you need to use multiple named extension modules, you can specify an array of modules with the :extend option.
    # In the case of name conflicts between methods in the modules, methods in modules later in the array supercede
    # those earlier in the array. Example:
    #
    #   class Account < ActiveRecord::Base
    #     has_many :people, :extend => [FindOrCreateByNameExtension, FindRecentExtension]
    #   end
    #
    # Some extensions can only be made to work with knowledge of the association proxy's internals.
    # Extensions can access relevant state using accessors on the association proxy:
    # 
    # * +proxy_owner+ - Returns the object the association is part of.
    # * +proxy_reflection+ - Returns the reflection object that describes the association.
    # * +proxy_target+ - Returns the associated object for belongs_to and has_one, or the collection of associated objects for has_many and has_and_belongs_to_many.
    #
    # === Association Join Models
    # 
    # Has Many associations can be configured with the :through option to use an explicit join model to retrieve the data.  This
    # operates similarly to a <tt>has_and_belongs_to_many</tt> association.  The advantage is that you're able to add validations,
    # callbacks, and extra attributes on the join model.  Consider the following schema:
    # 
    #   class Author < ActiveRecord::Base
    #     has_many :authorships
    #     has_many :books, :through => :authorships
    #   end
    # 
    #   class Authorship < ActiveRecord::Base
    #     belongs_to :author
    #     belongs_to :book
    #   end
    # 
    #   @author = Author.find :first
    #   @author.authorships.collect { |a| a.book } # selects all books that the author's authorships belong to.
    #   @author.books                              # selects all books by using the Authorship join model
    # 
    # You can also go through a has_many association on the join model:
    # 
    #   class Firm < ActiveRecord::Base
    #     has_many   :clients
    #     has_many   :invoices, :through => :clients
    #   end
    #   
    #   class Client < ActiveRecord::Base
    #     belongs_to :firm
    #     has_many   :invoices
    #   end
    #   
    #   class Invoice < ActiveRecord::Base
    #     belongs_to :client
    #   end
    #
    #   @firm = Firm.find :first
    #   @firm.clients.collect { |c| c.invoices }.flatten # select all invoices for all clients of the firm
    #   @firm.invoices                                   # selects all invoices by going through the Client join model.
    #
    # === Polymorphic Associations
    # 
    # Polymorphic associations on models are not restricted on what types of models they can be associated with.  Rather, they 
    # specify an interface that a has_many association must adhere to.
    # 
    #   class Asset < ActiveRecord::Base
    #     belongs_to :attachable, :polymorphic => true
    #   end
    # 
    #   class Post < ActiveRecord::Base
    #     has_many :assets, :as => :attachable         # The <tt>:as</tt> option specifies the polymorphic interface to use.
    #   end
    #
    #   @asset.attachable = @post
    # 
    # This works by using a type column in addition to a foreign key to specify the associated record.  In the Asset example, you'd need
    # an attachable_id integer column and an attachable_type string column.
    #
    # Using polymorphic associations in combination with single table inheritance (STI) is a little tricky. In order
    # for the associations to work as expected, ensure that you store the base model for the STI models in the 
    # type column of the polymorphic association. To continue with the asset example above, suppose there are guest posts
    # and member posts that use the posts table for STI. So there will be an additional 'type' column in the posts table.
    #
    #   class Asset < ActiveRecord::Base
    #     belongs_to :attachable, :polymorphic => true
    #     
    #     def attachable_type=(sType)
    #        super(sType.to_s.classify.constantize.base_class.to_s)
    #     end
    #   end
    # 
    #   class Post < ActiveRecord::Base
    #     # because we store "Post" in attachable_type now :dependent => :destroy will work
    #     has_many :assets, :as => :attachable, :dependent => :destroy
    #   end
    #
    #   class GuestPost < ActiveRecord::Base
    #   end
    #
    #   class MemberPost < ActiveRecord::Base
    #   end
    #
    # == Caching
    #
    # All of the methods are built on a simple caching principle that will keep the result of the last query around unless specifically
    # instructed not to. The cache is even shared across methods to make it even cheaper to use the macro-added methods without 
    # worrying too much about performance at the first go. Example:
    #
    #   project.milestones             # fetches milestones from the database
    #   project.milestones.size        # uses the milestone cache
    #   project.milestones.empty?      # uses the milestone cache
    #   project.milestones(true).size  # fetches milestones from the database
    #   project.milestones             # uses the milestone cache
    #
    # == Eager loading of associations
    #
    # Eager loading is a way to find objects of a certain class and a number of named associations along with it in a single SQL call. This is
    # one of the easiest ways of to prevent the dreaded 1+N problem in which fetching 100 posts that each needs to display their author
    # triggers 101 database queries. Through the use of eager loading, the 101 queries can be reduced to 1. Example:
    #
    #   class Post < ActiveRecord::Base
    #     belongs_to :author
    #     has_many   :comments
    #   end
    #
    # Consider the following loop using the class above:
    #
    #   for post in Post.find(:all)
    #     puts "Post:            " + post.title
    #     puts "Written by:      " + post.author.name
    #     puts "Last comment on: " + post.comments.first.created_on
    #   end 
    #
    # To iterate over these one hundred posts, we'll generate 201 database queries. Let's first just optimize it for retrieving the author:
    #
    #   for post in Post.find(:all, :include => :author)
    #
    # This references the name of the belongs_to association that also used the :author symbol, so the find will now weave in a join something
    # like this: LEFT OUTER JOIN authors ON authors.id = posts.author_id. Doing so will cut down the number of queries from 201 to 101.
    #
    # We can improve upon the situation further by referencing both associations in the finder with:
    #
    #   for post in Post.find(:all, :include => [ :author, :comments ])
    #
    # That'll add another join along the lines of: LEFT OUTER JOIN comments ON comments.post_id = posts.id. And we'll be down to 1 query.
    # But that shouldn't fool you to think that you can pull out huge amounts of data with no performance penalty just because you've reduced
    # the number of queries. The database still needs to send all the data to Active Record and it still needs to be processed. So it's no
    # catch-all for performance problems, but it's a great way to cut down on the number of queries in a situation as the one described above.
    # 
    # Since the eager loading pulls from multiple tables, you'll have to disambiguate any column references in both conditions and orders. So
    # :order => "posts.id DESC" will work while :order => "id DESC" will not. Because eager loading generates the SELECT statement too, the
    # :select option is ignored.
    #
    # You can use eager loading on multiple associations from the same table, but you cannot use those associations in orders and conditions
    # as there is currently not any way to disambiguate them. Eager loading will not pull additional attributes on join tables, so "rich
    # associations" with has_and_belongs_to_many are not a good fit for eager loading.
    # 
    # When eager loaded, conditions are interpolated in the context of the model class, not the model instance.  Conditions are lazily interpolated
    # before the actual model exists.
    # 
    # == Table Aliasing
    #
    # ActiveRecord uses table aliasing in the case that a table is referenced multiple times in a join.  If a table is referenced only once,
    # the standard table name is used.  The second time, the table is aliased as #{reflection_name}_#{parent_table_name}.  Indexes are appended
    # for any more successive uses of the table name.
    # 
    #   Post.find :all, :include => :comments
    #   # => SELECT ... FROM posts LEFT OUTER JOIN comments ON ...
    #   Post.find :all, :include => :special_comments # STI
    #   # => SELECT ... FROM posts LEFT OUTER JOIN comments ON ... AND comments.type = 'SpecialComment'
    #   Post.find :all, :include => [:comments, :special_comments] # special_comments is the reflection name, posts is the parent table name
    #   # => SELECT ... FROM posts LEFT OUTER JOIN comments ON ... LEFT OUTER JOIN comments special_comments_posts
    # 
    # Acts as tree example:
    # 
    #   TreeMixin.find :all, :include => :children
    #   # => SELECT ... FROM mixins LEFT OUTER JOIN mixins childrens_mixins ...
    #   TreeMixin.find :all, :include => {:children => :parent} # using cascading eager includes
    #   # => SELECT ... FROM mixins LEFT OUTER JOIN mixins childrens_mixins ... 
    #                               LEFT OUTER JOIN parents_mixins ...
    #   TreeMixin.find :all, :include => {:children => {:parent => :children}} 
    #   # => SELECT ... FROM mixins LEFT OUTER JOIN mixins childrens_mixins ... 
    #                               LEFT OUTER JOIN parents_mixins ... 
    # LEFT OUTER JOIN mixins childrens_mixins_2
    # 
    # Has and Belongs to Many join tables use the same idea, but add a _join suffix:
    # 
    #   Post.find :all, :include => :categories
    #   # => SELECT ... FROM posts LEFT OUTER JOIN categories_posts ... LEFT OUTER JOIN categories ...
    #   Post.find :all, :include => {:categories => :posts}
    #   # => SELECT ... FROM posts LEFT OUTER JOIN categories_posts ... LEFT OUTER JOIN categories ...
    #                              LEFT OUTER JOIN categories_posts posts_categories_join LEFT OUTER JOIN posts posts_categories
    #   Post.find :all, :include => {:categories => {:posts => :categories}}
    #   # => SELECT ... FROM posts LEFT OUTER JOIN categories_posts ... LEFT OUTER JOIN categories ...
    #                              LEFT OUTER JOIN categories_posts posts_categories_join LEFT OUTER JOIN posts posts_categories
    #                              LEFT OUTER JOIN categories_posts categories_posts_join LEFT OUTER JOIN categories categories_posts
    # 
    # If you wish to specify your own custom joins using a :joins option, those table names will take precedence over the eager associations..
    # 
    #   Post.find :all, :include => :comments, :joins => "inner join comments ..."
    #   # => SELECT ... FROM posts LEFT OUTER JOIN comments_posts ON ... INNER JOIN comments ...
    #   Post.find :all, :include => [:comments, :special_comments], :joins => "inner join comments ..."
    #   # => SELECT ... FROM posts LEFT OUTER JOIN comments comments_posts ON ... 
    #                              LEFT OUTER JOIN comments special_comments_posts ...
    #                              INNER JOIN comments ...
    # 
    # Table aliases are automatically truncated according to the maximum length of table identifiers according to the specific database.
    # 
    # == Modules
    #
    # By default, associations will look for objects within the current module scope. Consider:
    #
    #   module MyApplication
    #     module Business
    #       class Firm < ActiveRecord::Base
    #          has_many :clients
    #        end
    #
    #       class Company < ActiveRecord::Base; end
    #     end
    #   end
    #
    # When Firm#clients is called, it'll in turn call <tt>MyApplication::Business::Company.find(firm.id)</tt>. If you want to associate
    # with a class in another module scope this can be done by specifying the complete class name, such as:
    #
    #   module MyApplication
    #     module Business
    #       class Firm < ActiveRecord::Base; end
    #     end
    #
    #     module Billing
    #       class Account < ActiveRecord::Base
    #         belongs_to :firm, :class_name => "MyApplication::Business::Firm"
    #       end
    #     end
    #   end
    #
    # == Type safety with ActiveRecord::AssociationTypeMismatch
    #
    # If you attempt to assign an object to an association that doesn't match the inferred or specified <tt>:class_name</tt>, you'll
    # get a ActiveRecord::AssociationTypeMismatch.
    #
    # == Options
    #
    # All of the association macros can be specialized through options which makes more complex cases than the simple and guessable ones
    # possible.
    module ClassMethods
      # Adds the following methods for retrieval and query of collections of associated objects.
      # +collection+ is replaced with the symbol passed as the first argument, so 
      # <tt>has_many :clients</tt> would add among others <tt>clients.empty?</tt>.
      # * <tt>collection(force_reload = false)</tt> - returns an array of all the associated objects.
      #   An empty array is returned if none are found.
      # * <tt>collection<<(object, ...)</tt> - adds one or more objects to the collection by setting their foreign keys to the collection's primary key.
      # * <tt>collection.delete(object, ...)</tt> - removes one or more objects from the collection by setting their foreign keys to NULL.  
      #   This will also destroy the objects if they're declared as belongs_to and dependent on this model.
      # * <tt>collection=objects</tt> - replaces the collections content by deleting and adding objects as appropriate.
      # * <tt>collection_singular_ids</tt> - returns an array of the associated objects ids
      # * <tt>collection_singular_ids=ids</tt> - replace the collection by the objects identified by the primary keys in +ids+
      # * <tt>collection.clear</tt> - removes every object from the collection. This destroys the associated objects if they
      #   are associated with <tt>:dependent => :destroy</tt>, deletes them directly from the database if <tt>:dependent => :delete_all</tt>,
      #   and sets their foreign keys to NULL otherwise.
      # * <tt>collection.empty?</tt> - returns true if there are no associated objects.
      # * <tt>collection.size</tt> - returns the number of associated objects.
      # * <tt>collection.find</tt> - finds an associated object according to the same rules as Base.find.
      # * <tt>collection.build(attributes = {})</tt> - returns a new object of the collection type that has been instantiated
      #   with +attributes+ and linked to this object through a foreign key but has not yet been saved. *Note:* This only works if an 
      #   associated object already exists, not if it's nil!
      # * <tt>collection.create(attributes = {})</tt> - returns a new object of the collection type that has been instantiated
      #   with +attributes+ and linked to this object through a foreign key and that has already been saved (if it passed the validation).
      #   *Note:* This only works if an associated object already exists, not if it's nil!
      #
      # Example: A Firm class declares <tt>has_many :clients</tt>, which will add:
      # * <tt>Firm#clients</tt> (similar to <tt>Clients.find :all, :conditions => "firm_id = #{id}"</tt>)
      # * <tt>Firm#clients<<</tt>
      # * <tt>Firm#clients.delete</tt>
      # * <tt>Firm#clients=</tt>
      # * <tt>Firm#client_ids</tt>
      # * <tt>Firm#client_ids=</tt>
      # * <tt>Firm#clients.clear</tt>
      # * <tt>Firm#clients.empty?</tt> (similar to <tt>firm.clients.size == 0</tt>)
      # * <tt>Firm#clients.size</tt> (similar to <tt>Client.count "firm_id = #{id}"</tt>)
      # * <tt>Firm#clients.find</tt> (similar to <tt>Client.find(id, :conditions => "firm_id = #{id}")</tt>)
      # * <tt>Firm#clients.build</tt> (similar to <tt>Client.new("firm_id" => id)</tt>)
      # * <tt>Firm#clients.create</tt> (similar to <tt>c = Client.new("firm_id" => id); c.save; c</tt>)
      # The declaration can also include an options hash to specialize the behavior of the association.
      # 
      # Options are:
      # * <tt>:class_name</tt>  - specify the class name of the association. Use it only if that name can't be inferred
      #   from the association name. So <tt>has_many :products</tt> will by default be linked to the +Product+ class, but
      #   if the real class name is +SpecialProduct+, you'll have to specify it with this option.
      # * <tt>:conditions</tt>  - specify the conditions that the associated objects must meet in order to be included as a "WHERE"
      #   sql fragment, such as "price > 5 AND name LIKE 'B%'".
      # * <tt>:order</tt>       - specify the order in which the associated objects are returned as a "ORDER BY" sql fragment,
      #   such as "last_name, first_name DESC"
      # * <tt>:group</tt>       - specify the attribute by which the associated objects are returned as a "GROUP BY" sql fragment,
      #   such as "category"      
      # * <tt>:foreign_key</tt> - specify the foreign key used for the association. By default this is guessed to be the name
      #   of this class in lower-case and "_id" suffixed. So a +Person+ class that makes a has_many association will use "person_id"
      #   as the default foreign_key.
      # * <tt>:dependent</tt>   - if set to :destroy all the associated objects are destroyed
      #   alongside this object by calling their destroy method.  If set to :delete_all all associated
      #   objects are deleted *without* calling their destroy method.  If set to :nullify all associated
      #   objects' foreign keys are set to NULL *without* calling their save callbacks.
      #   NOTE: :dependent => true is deprecated and has been replaced with :dependent => :destroy. 
      #   May not be set if :exclusively_dependent is also set.
      # * <tt>:exclusively_dependent</tt>   - Deprecated; equivalent to :dependent => :delete_all. If set to true all
      #   the associated object are deleted in one SQL statement without having their
      #   before_destroy callback run. This should only be used on associations that depend solely on this class and don't need to do any
      #   clean-up in before_destroy. The upside is that it's much faster, especially if there's a counter_cache involved.
      #   May not be set if :dependent is also set.
      # * <tt>:finder_sql</tt>  - specify a complete SQL statement to fetch the association. This is a good way to go for complex
      #   associations that depend on multiple tables. Note: When this option is used, +find_in_collection+ is _not_ added.
      # * <tt>:counter_sql</tt>  - specify a complete SQL statement to fetch the size of the association. If +:finder_sql+ is
      #   specified but +:counter_sql+, +:counter_sql+ will be generated by replacing SELECT ... FROM with SELECT COUNT(*) FROM.
      # * <tt>:extend</tt>  - specify a named module for extending the proxy, see "Association extensions".
      # * <tt>:include</tt>  - specify second-order associations that should be eager loaded when the collection is loaded.
      # * <tt>:group</tt>: An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause.
      # * <tt>:limit</tt>: An integer determining the limit on the number of rows that should be returned.
      # * <tt>:offset</tt>: An integer determining the offset from where the rows should be fetched. So at 5, it would skip the first 4 rows.
      # * <tt>:select</tt>: By default, this is * as in SELECT * FROM, but can be changed if you for example want to do a join, but not
      #   include the joined columns.
      # * <tt>:as</tt>: Specifies a polymorphic interface (See #belongs_to).
      # * <tt>:through</tt>: Specifies a Join Model to perform the query through.  Options for <tt>:class_name</tt> and <tt>:foreign_key</tt> 
      #   are ignored, as the association uses the source reflection.  You can only use a <tt>:through</tt> query through a <tt>belongs_to</tt>
      #   or <tt>has_many</tt> association.
      # * <tt>:source</tt>: Specifies the source association name used by <tt>has_many :through</tt> queries.  Only use it if the name cannot be 
      #   inferred from the association.  <tt>has_many :subscribers, :through => :subscriptions</tt> will look for either +:subscribers+ or
      #   +:subscriber+ on +Subscription+, unless a +:source+ is given.
      # * <tt>:source_type</tt>: Specifies type of the source association used by <tt>has_many :through</tt> queries where the source association
      #   is a polymorphic belongs_to.
      # * <tt>:uniq</tt> - if set to true, duplicates will be omitted from the collection. Useful in conjunction with :through.
      #
      # Option examples:
      #   has_many :comments, :order => "posted_on"
      #   has_many :comments, :include => :author
      #   has_many :people, :class_name => "Person", :conditions => "deleted = 0", :order => "name"
      #   has_many :tracks, :order => "position", :dependent => :destroy
      #   has_many :comments, :dependent => :nullify
      #   has_many :tags, :as => :taggable
      #   has_many :subscribers, :through => :subscriptions, :source => :user
      #   has_many :subscribers, :class_name => "Person", :finder_sql =>
      #       'SELECT DISTINCT people.* ' +
      #       'FROM people p, post_subscriptions ps ' +
      #       'WHERE ps.post_id = #{id} AND ps.person_id = p.id ' +
      #       'ORDER BY p.first_name'
      def has_many(association_id, options = {}, &extension)
        reflection = create_has_many_reflection(association_id, options, &extension)

        configure_dependency_for_has_many(reflection)

        if options[:through]
          collection_reader_method(reflection, HasManyThroughAssociation)
        else
          add_multiple_associated_save_callbacks(reflection.name)
          add_association_callbacks(reflection.name, reflection.options)
          collection_accessor_methods(reflection, HasManyAssociation)
        end

        add_deprecated_api_for_has_many(reflection.name)
      end

      # Adds the following methods for retrieval and query of a single associated object.
      # +association+ is replaced with the symbol passed as the first argument, so 
      # <tt>has_one :manager</tt> would add among others <tt>manager.nil?</tt>.
      # * <tt>association(force_reload = false)</tt> - returns the associated object. Nil is returned if none is found.
      # * <tt>association=(associate)</tt> - assigns the associate object, extracts the primary key, sets it as the foreign key, 
      #   and saves the associate object.
      # * <tt>association.nil?</tt> - returns true if there is no associated object.
      # * <tt>build_association(attributes = {})</tt> - returns a new object of the associated type that has been instantiated
      #   with +attributes+ and linked to this object through a foreign key but has not yet been saved. Note: This ONLY works if
      #   an association already exists. It will NOT work if the association is nil.
      # * <tt>create_association(attributes = {})</tt> - returns a new object of the associated type that has been instantiated
      #   with +attributes+ and linked to this object through a foreign key and that has already been saved (if it passed the validation).
      #
      # Example: An Account class declares <tt>has_one :beneficiary</tt>, which will add:
      # * <tt>Account#beneficiary</tt> (similar to <tt>Beneficiary.find(:first, :conditions => "account_id = #{id}")</tt>)
      # * <tt>Account#beneficiary=(beneficiary)</tt> (similar to <tt>beneficiary.account_id = account.id; beneficiary.save</tt>)
      # * <tt>Account#beneficiary.nil?</tt>
      # * <tt>Account#build_beneficiary</tt> (similar to <tt>Beneficiary.new("account_id" => id)</tt>)
      # * <tt>Account#create_beneficiary</tt> (similar to <tt>b = Beneficiary.new("account_id" => id); b.save; b</tt>)
      #
      # The declaration can also include an options hash to specialize the behavior of the association.
      # 
      # Options are:
      # * <tt>:class_name</tt>  - specify the class name of the association. Use it only if that name can't be inferred
      #   from the association name. So <tt>has_one :manager</tt> will by default be linked to the +Manager+ class, but
      #   if the real class name is +Person+, you'll have to specify it with this option.
      # * <tt>:conditions</tt>  - specify the conditions that the associated object must meet in order to be included as a "WHERE"
      #   sql fragment, such as "rank = 5".
      # * <tt>:order</tt>       - specify the order from which the associated object will be picked at the top. Specified as
      #    an "ORDER BY" sql fragment, such as "last_name, first_name DESC"
      # * <tt>:dependent</tt>   - if set to :destroy (or true) the associated object is destroyed when this object is. If set to
      #   :delete the associated object is deleted *without* calling its destroy method. If set to :nullify the associated
      #   object's foreign key is set to NULL. Also, association is assigned.
      # * <tt>:foreign_key</tt> - specify the foreign key used for the association. By default this is guessed to be the name
      #   of this class in lower-case and "_id" suffixed. So a +Person+ class that makes a has_one association will use "person_id"
      #   as the default foreign_key.
      # * <tt>:include</tt>  - specify second-order associations that should be eager loaded when this object is loaded.
      # * <tt>:as</tt>: Specifies a polymorphic interface (See #belongs_to).
            #
      # Option examples:
      #   has_one :credit_card, :dependent => :destroy  # destroys the associated credit card
      #   has_one :credit_card, :dependent => :nullify  # updates the associated records foriegn key value to null rather than destroying it
      #   has_one :last_comment, :class_name => "Comment", :order => "posted_on"
      #   has_one :project_manager, :class_name => "Person", :conditions => "role = 'project_manager'"
      #   has_one :attachment, :as => :attachable
      def has_one(association_id, options = {})
        reflection = create_has_one_reflection(association_id, options)

        module_eval do
          after_save <<-EOF
            association = instance_variable_get("@#{reflection.name}")
            if !association.nil? && (new_record? || association.new_record? || association["#{reflection.primary_key_name}"] != id)
              association["#{reflection.primary_key_name}"] = id
              association.save(true)
            end
          EOF
        end
      
        association_accessor_methods(reflection, HasOneAssociation)
        association_constructor_method(:build,  reflection, HasOneAssociation)
        association_constructor_method(:create, reflection, HasOneAssociation)
        
        configure_dependency_for_has_one(reflection)

        # deprecated api
        deprecated_has_association_method(reflection.name)
        deprecated_association_comparison_method(reflection.name, reflection.class_name)
      end

      # Adds the following methods for retrieval and query for a single associated object that this object holds an id to.
      # +association+ is replaced with the symbol passed as the first argument, so 
      # <tt>belongs_to :author</tt> would add among others <tt>author.nil?</tt>.
      # * <tt>association(force_reload = false)</tt> - returns the associated object. Nil is returned if none is found.
      # * <tt>association=(associate)</tt> - assigns the associate object, extracts the primary key, and sets it as the foreign key.
      # * <tt>association.nil?</tt> - returns true if there is no associated object.
      # * <tt>build_association(attributes = {})</tt> - returns a new object of the associated type that has been instantiated
      #   with +attributes+ and linked to this object through a foreign key but has not yet been saved.
      # * <tt>create_association(attributes = {})</tt> - returns a new object of the associated type that has been instantiated
      #   with +attributes+ and linked to this object through a foreign key and that has already been saved (if it passed the validation).
      #
      # Example: A Post class declares <tt>belongs_to :author</tt>, which will add:
      # * <tt>Post#author</tt> (similar to <tt>Author.find(author_id)</tt>)
      # * <tt>Post#author=(author)</tt> (similar to <tt>post.author_id = author.id</tt>)
      # * <tt>Post#author?</tt> (similar to <tt>post.author == some_author</tt>)
      # * <tt>Post#author.nil?</tt>
      # * <tt>Post#build_author</tt> (similar to <tt>post.author = Author.new</tt>)
      # * <tt>Post#create_author</tt> (similar to <tt>post.author = Author.new; post.author.save; post.author</tt>)
      # The declaration can also include an options hash to specialize the behavior of the association.
      # 
      # Options are:
      # * <tt>:class_name</tt>  - specify the class name of the association. Use it only if that name can't be inferred
      #   from the association name. So <tt>has_one :author</tt> will by default be linked to the +Author+ class, but
      #   if the real class name is +Person+, you'll have to specify it with this option.
      # * <tt>:conditions</tt>  - specify the conditions that the associated object must meet in order to be included as a "WHERE"
      #   sql fragment, such as "authorized = 1".
      # * <tt>:order</tt>       - specify the order from which the associated object will be picked at the top. Specified as
      #   an "ORDER BY" sql fragment, such as "last_name, first_name DESC"
      # * <tt>:foreign_key</tt> - specify the foreign key used for the association. By default this is guessed to be the name
      #   of the associated class in lower-case and "_id" suffixed. So a +Person+ class that makes a belongs_to association to a
      #   +Boss+ class will use "boss_id" as the default foreign_key.
      # * <tt>:counter_cache</tt> - caches the number of belonging objects on the associate class through use of increment_counter 
      #   and decrement_counter. The counter cache is incremented when an object of this class is created and decremented when it's
      #   destroyed. This requires that a column named "#{table_name}_count" (such as comments_count for a belonging Comment class)
      #   is used on the associate class (such as a Post class). You can also specify a custom counter cache column by given that
      #   name instead of a true/false value to this option (e.g., <tt>:counter_cache => :my_custom_counter</tt>.)
      # * <tt>:include</tt>  - specify second-order associations that should be eager loaded when this object is loaded.
      # * <tt>:polymorphic</tt> - specify this association is a polymorphic association by passing true.
      #
      # Option examples:
      #   belongs_to :firm, :foreign_key => "client_of"
      #   belongs_to :author, :class_name => "Person", :foreign_key => "author_id"
      #   belongs_to :valid_coupon, :class_name => "Coupon", :foreign_key => "coupon_id", 
      #              :conditions => 'discounts > #{payments_count}'
      #   belongs_to :attachable, :polymorphic => true
      def belongs_to(association_id, options = {})
        if options.include?(:class_name) && !options.include?(:foreign_key)
          ::ActiveSupport::Deprecation.warn(
          "The inferred foreign_key name will change in Rails 2.0 to use the association name instead of its class name when they differ.  When using :class_name in belongs_to, use the :foreign_key option to explicitly set the key name to avoid problems in the transition.",
          caller)
        end
        
        reflection = create_belongs_to_reflection(association_id, options)
        
        if reflection.options[:polymorphic]
          association_accessor_methods(reflection, BelongsToPolymorphicAssociation)

          module_eval do
            before_save <<-EOF
              association = instance_variable_get("@#{reflection.name}")
              if association && association.target
                if association.new_record?
                  association.save(true)
                end
                
                if association.updated?
                  self["#{reflection.primary_key_name}"] = association.id
                  self["#{reflection.options[:foreign_type]}"] = association.class.base_class.name.to_s
                end
              end
            EOF
          end
        else
          association_accessor_methods(reflection, BelongsToAssociation)
          association_constructor_method(:build,  reflection, BelongsToAssociation)
          association_constructor_method(:create, reflection, BelongsToAssociation)

          module_eval do
            before_save <<-EOF
              association = instance_variable_get("@#{reflection.name}")
              if !association.nil? 
                if association.new_record?
                  association.save(true)
                end
                
                if association.updated?
                  self["#{reflection.primary_key_name}"] = association.id
                end
              end            
            EOF
          end
      
          # deprecated api
          deprecated_has_association_method(reflection.name)
          deprecated_association_comparison_method(reflection.name, reflection.class_name)
        end

        # Create the callbacks to update counter cache
        if options[:counter_cache]
          cache_column = options[:counter_cache] == true ?
            "#{self.to_s.underscore.pluralize}_count" :
            options[:counter_cache]

          module_eval(
            "after_create '#{reflection.name}.class.increment_counter(\"#{cache_column}\", #{reflection.primary_key_name})" +
            " unless #{reflection.name}.nil?'"
          )

          module_eval(
            "before_destroy '#{reflection.name}.class.decrement_counter(\"#{cache_column}\", #{reflection.primary_key_name})" +
            " unless #{reflection.name}.nil?'"
          )          
        end
      end

      # Associates two classes via an intermediate join table.  Unless the join table is explicitly specified as
      # an option, it is guessed using the lexical order of the class names. So a join between Developer and Project
      # will give the default join table name of "developers_projects" because "D" outranks "P".  Note that this precedence
      # is calculated using the <tt><</tt> operator for <tt>String</tt>.  This means that if the strings are of different lengths, 
      # and the strings are equal when compared up to the shortest length, then the longer string is considered of higher
      # lexical precedence than the shorter one.  For example, one would expect the tables <tt>paper_boxes</tt> and <tt>papers</tt> 
      # to generate a join table name of <tt>papers_paper_boxes</tt> because of the length of the name <tt>paper_boxes</tt>,
      # but it in fact generates a join table name of <tt>paper_boxes_papers</tt>.  Be aware of this caveat, and use the 
      # custom <tt>join_table</tt> option if you need to.
      #
      # Deprecated: Any additional fields added to the join table will be placed as attributes when pulling records out through
      # has_and_belongs_to_many associations. Records returned from join tables with additional attributes will be marked as
      # ReadOnly (because we can't save changes to the additional attrbutes). It's strongly recommended that you upgrade any
      # associations with attributes to a real join model (see introduction).
      #
      # Adds the following methods for retrieval and query.
      # +collection+ is replaced with the symbol passed as the first argument, so 
      # <tt>has_and_belongs_to_many :categories</tt> would add among others <tt>categories.empty?</tt>.
      # * <tt>collection(force_reload = false)</tt> - returns an array of all the associated objects.
      #   An empty array is returned if none is found.
      # * <tt>collection<<(object, ...)</tt> - adds one or more objects to the collection by creating associations in the join table 
      #   (collection.push and collection.concat are aliases to this method).
      # * <tt>collection.push_with_attributes(object, join_attributes)</tt> - adds one to the collection by creating an association in the join table that
      #   also holds the attributes from <tt>join_attributes</tt> (should be a hash with the column names as keys). This can be used to have additional
      #   attributes on the join, which will be injected into the associated objects when they are retrieved through the collection.
      #   (collection.concat_with_attributes is an alias to this method). This method is now deprecated.
      # * <tt>collection.delete(object, ...)</tt> - removes one or more objects from the collection by removing their associations from the join table.  
      #   This does not destroy the objects.
      # * <tt>collection=objects</tt> - replaces the collections content by deleting and adding objects as appropriate.
      # * <tt>collection_singular_ids</tt> - returns an array of the associated objects ids
      # * <tt>collection_singular_ids=ids</tt> - replace the collection by the objects identified by the primary keys in +ids+
      # * <tt>collection.clear</tt> - removes every object from the collection. This does not destroy the objects.
      # * <tt>collection.empty?</tt> - returns true if there are no associated objects.
      # * <tt>collection.size</tt> - returns the number of associated objects.
      # * <tt>collection.find(id)</tt> - finds an associated object responding to the +id+ and that
      #   meets the condition that it has to be associated with this object.
      # * <tt>collection.build(attributes = {})</tt> - returns a new object of the collection type that has been instantiated
      #   with +attributes+ and linked to this object through the join table but has not yet been saved.
      # * <tt>collection.create(attributes = {})</tt> - returns a new object of the collection type that has been instantiated
      #   with +attributes+ and linked to this object through the join table and that has already been saved (if it passed the validation).
      #
      # Example: An Developer class declares <tt>has_and_belongs_to_many :projects</tt>, which will add:
      # * <tt>Developer#projects</tt>
      # * <tt>Developer#projects<<</tt>
      # * <tt>Developer#projects.delete</tt>
      # * <tt>Developer#projects=</tt>
      # * <tt>Developer#project_ids</tt>
      # * <tt>Developer#project_ids=</tt>
      # * <tt>Developer#projects.clear</tt>
      # * <tt>Developer#projects.empty?</tt>
      # * <tt>Developer#projects.size</tt>
      # * <tt>Developer#projects.find(id)</tt>
      # * <tt>Developer#projects.build</tt> (similar to <tt>Project.new("project_id" => id)</tt>)
      # * <tt>Developer#projects.create</tt> (similar to <tt>c = Project.new("project_id" => id); c.save; c</tt>)
      # The declaration may include an options hash to specialize the behavior of the association.
      # 
      # Options are:
      # * <tt>:class_name</tt> - specify the class name of the association. Use it only if that name can't be inferred
      #   from the association name. So <tt>has_and_belongs_to_many :projects</tt> will by default be linked to the 
      #   +Project+ class, but if the real class name is +SuperProject+, you'll have to specify it with this option.
      # * <tt>:join_table</tt> - specify the name of the join table if the default based on lexical order isn't what you want.
      #   WARNING: If you're overwriting the table name of either class, the table_name method MUST be declared underneath any
      #   has_and_belongs_to_many declaration in order to work.
      # * <tt>:foreign_key</tt> - specify the foreign key used for the association. By default this is guessed to be the name
      #   of this class in lower-case and "_id" suffixed. So a +Person+ class that makes a has_and_belongs_to_many association
      #   will use "person_id" as the default foreign_key.
      # * <tt>:association_foreign_key</tt> - specify the association foreign key used for the association. By default this is
      #   guessed to be the name of the associated class in lower-case and "_id" suffixed. So if the associated class is +Project+,
      #   the has_and_belongs_to_many association will use "project_id" as the default association foreign_key.
      # * <tt>:conditions</tt>  - specify the conditions that the associated object must meet in order to be included as a "WHERE"
      #   sql fragment, such as "authorized = 1".
      # * <tt>:order</tt> - specify the order in which the associated objects are returned as a "ORDER BY" sql fragment, such as "last_name, first_name DESC"
      # * <tt>:uniq</tt> - if set to true, duplicate associated objects will be ignored by accessors and query methods
      # * <tt>:finder_sql</tt> - overwrite the default generated SQL used to fetch the association with a manual one
      # * <tt>:delete_sql</tt> - overwrite the default generated SQL used to remove links between the associated 
      #   classes with a manual one
      # * <tt>:insert_sql</tt> - overwrite the default generated SQL used to add links between the associated classes
      #   with a manual one
      # * <tt>:extend</tt>  - anonymous module for extending the proxy, see "Association extensions".
      # * <tt>:include</tt>  - specify second-order associations that should be eager loaded when the collection is loaded.
      # * <tt>:group</tt>: An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause.
      # * <tt>:limit</tt>: An integer determining the limit on the number of rows that should be returned.
      # * <tt>:offset</tt>: An integer determining the offset from where the rows should be fetched. So at 5, it would skip the first 4 rows.
      # * <tt>:select</tt>: By default, this is * as in SELECT * FROM, but can be changed if you for example want to do a join, but not
      #   include the joined columns.
      #
      # Option examples:
      #   has_and_belongs_to_many :projects
      #   has_and_belongs_to_many :projects, :include => [ :milestones, :manager ]
      #   has_and_belongs_to_many :nations, :class_name => "Country"
      #   has_and_belongs_to_many :categories, :join_table => "prods_cats"
      #   has_and_belongs_to_many :active_projects, :join_table => 'developers_projects', :delete_sql => 
      #   'DELETE FROM developers_projects WHERE active=1 AND developer_id = #{id} AND project_id = #{record.id}'
      def has_and_belongs_to_many(association_id, options = {}, &extension)
        reflection = create_has_and_belongs_to_many_reflection(association_id, options, &extension)
        
        add_multiple_associated_save_callbacks(reflection.name)
        collection_accessor_methods(reflection, HasAndBelongsToManyAssociation)

        # Don't use a before_destroy callback since users' before_destroy
        # callbacks will be executed after the association is wiped out.
        old_method = "destroy_without_habtm_shim_for_#{reflection.name}"
        class_eval <<-end_eval
          alias_method :#{old_method}, :destroy_without_callbacks
          def destroy_without_callbacks
            #{reflection.name}.clear
            #{old_method}
          end
        end_eval

        add_association_callbacks(reflection.name, options)
        
        # deprecated api
        deprecated_collection_count_method(reflection.name)
        deprecated_add_association_relation(reflection.name)
        deprecated_remove_association_relation(reflection.name)
        deprecated_has_collection_method(reflection.name)
      end

      private
        # Generate a join table name from two provided tables names.
        # The order of names in join name is determined by lexical precedence.
        #   join_table_name("members", "clubs")
        #   => "clubs_members"
        #   join_table_name("members", "special_clubs")
        #   => "members_special_clubs"
        def join_table_name(first_table_name, second_table_name)
          if first_table_name < second_table_name
            join_table = "#{first_table_name}_#{second_table_name}"
          else
            join_table = "#{second_table_name}_#{first_table_name}"
          end

          table_name_prefix + join_table + table_name_suffix
        end
      
        def association_accessor_methods(reflection, association_proxy_class)
          define_method(reflection.name) do |*params|
            force_reload = params.first unless params.empty?
            association = instance_variable_get("@#{reflection.name}")

            if association.nil? || force_reload
              association = association_proxy_class.new(self, reflection)
              retval = association.reload
              if retval.nil? and association_proxy_class == BelongsToAssociation
                instance_variable_set("@#{reflection.name}", nil)
                return nil
              end
              instance_variable_set("@#{reflection.name}", association)
            end

            association.target.nil? ? nil : association
          end

          define_method("#{reflection.name}=") do |new_value|
            association = instance_variable_get("@#{reflection.name}")
            if association.nil?
              association = association_proxy_class.new(self, reflection)
            end

            association.replace(new_value)

            unless new_value.nil?
              instance_variable_set("@#{reflection.name}", association)
            else
              instance_variable_set("@#{reflection.name}", nil)
              return nil
            end

            association
          end

          define_method("set_#{reflection.name}_target") do |target|
            return if target.nil? and association_proxy_class == BelongsToAssociation
            association = association_proxy_class.new(self, reflection)
            association.target = target
            instance_variable_set("@#{reflection.name}", association)
          end
        end

        def collection_reader_method(reflection, association_proxy_class)
          define_method(reflection.name) do |*params|
            force_reload = params.first unless params.empty?
            association = instance_variable_get("@#{reflection.name}")

            unless association.respond_to?(:loaded?)
              association = association_proxy_class.new(self, reflection)
              instance_variable_set("@#{reflection.name}", association)
            end

            association.reload if force_reload

            association
          end
        end

        def collection_accessor_methods(reflection, association_proxy_class)
          collection_reader_method(reflection, association_proxy_class)

          define_method("#{reflection.name}=") do |new_value|
            # Loads proxy class instance (defined in collection_reader_method) if not already loaded
            association = send(reflection.name) 
            association.replace(new_value)
            association
          end

          define_method("#{reflection.name.to_s.singularize}_ids") do
            send(reflection.name).map(&:id)
          end

          define_method("#{reflection.name.to_s.singularize}_ids=") do |new_value|
            ids = (new_value || []).reject { |nid| nid.blank? }
            send("#{reflection.name}=", reflection.class_name.constantize.find(ids))
          end
        end

        def add_multiple_associated_save_callbacks(association_name)
          method_name = "validate_associated_records_for_#{association_name}".to_sym
          define_method(method_name) do
            association = instance_variable_get("@#{association_name}")
            if association.respond_to?(:loaded?)
              if new_record?
                association
              else
                association.select { |record| record.new_record? }
              end.each do |record|
                errors.add "#{association_name}" unless record.valid?
              end
            end
          end

          validate method_name
          before_save("@new_record_before_save = new_record?; true")

          after_callback = <<-end_eval
            association = instance_variable_get("@#{association_name}")
            
            if association.respond_to?(:loaded?)
              if @new_record_before_save
                records_to_save = association
              else
                records_to_save = association.select { |record| record.new_record? }
              end
              records_to_save.each { |record| association.send(:insert_record, record) }
              association.send(:construct_sql)   # reconstruct the SQL queries now that we know the owner's id
            end
          end_eval
                
          # Doesn't use after_save as that would save associations added in after_create/after_update twice
          after_create(after_callback)
          after_update(after_callback)
        end

        def association_constructor_method(constructor, reflection, association_proxy_class)
          define_method("#{constructor}_#{reflection.name}") do |*params|
            attributees      = params.first unless params.empty?
            replace_existing = params[1].nil? ? true : params[1]
            association      = instance_variable_get("@#{reflection.name}")

            if association.nil?
              association = association_proxy_class.new(self, reflection)
              instance_variable_set("@#{reflection.name}", association)
            end

            if association_proxy_class == HasOneAssociation
              association.send(constructor, attributees, replace_existing)
            else
              association.send(constructor, attributees)
            end
          end
        end
        
        def find_with_associations(options = {})
          catch :invalid_query do
            join_dependency = JoinDependency.new(self, merge_includes(scope(:find, :include), options[:include]), options[:joins])
            rows = select_all_rows(options, join_dependency)
            return join_dependency.instantiate(rows)
          end
          []
        end

        def configure_dependency_for_has_many(reflection)
          if reflection.options[:dependent] == true
            ::ActiveSupport::Deprecation.warn("The :dependent => true option is deprecated and will be removed from Rails 2.0.  Please use :dependent => :destroy instead.  See http://www.rubyonrails.org/deprecation for details.", caller)
          end

          if reflection.options[:dependent] && reflection.options[:exclusively_dependent]
            raise ArgumentError, ':dependent and :exclusively_dependent are mutually exclusive options.  You may specify one or the other.'
          end

          if reflection.options[:exclusively_dependent]
            reflection.options[:dependent] = :delete_all
            ::ActiveSupport::Deprecation.warn("The :exclusively_dependent option is deprecated and will be removed from Rails 2.0.  Please use :dependent => :delete_all instead.  See http://www.rubyonrails.org/deprecation for details.", caller)
          end

          # See HasManyAssociation#delete_records.  Dependent associations
          # delete children, otherwise foreign key is set to NULL.

          # Add polymorphic type if the :as option is present
          dependent_conditions = %(#{reflection.primary_key_name} = \#{record.quoted_id})
          if reflection.options[:as]
            dependent_conditions += " AND #{reflection.options[:as]}_type = '#{base_class.name}'"
          end

          case reflection.options[:dependent]
            when :destroy, true
              module_eval "before_destroy '#{reflection.name}.each { |o| o.destroy }'"
            when :delete_all
              module_eval "before_destroy { |record| #{reflection.class_name}.delete_all(%(#{dependent_conditions})) }"
            when :nullify
              module_eval "before_destroy { |record| #{reflection.class_name}.update_all(%(#{reflection.primary_key_name} = NULL),  %(#{dependent_conditions})) }"
            when nil, false
              # pass
            else
              raise ArgumentError, 'The :dependent option expects either :destroy, :delete_all, or :nullify'
          end
        end

        def configure_dependency_for_has_one(reflection)
          case reflection.options[:dependent]
            when :destroy, true
              module_eval "before_destroy '#{reflection.name}.destroy unless #{reflection.name}.nil?'"
            when :delete
              module_eval "before_destroy '#{reflection.class_name}.delete(#{reflection.name}.id) unless #{reflection.name}.nil?'"
            when :nullify
              module_eval "before_destroy '#{reflection.name}.update_attribute(\"#{reflection.primary_key_name}\", nil) unless #{reflection.name}.nil?'"
            when nil, false
              # pass
            else
              raise ArgumentError, "The :dependent option expects either :destroy, :delete or :nullify."
          end
        end
        
        
        def add_deprecated_api_for_has_many(association_name)
          deprecated_collection_count_method(association_name)
          deprecated_add_association_relation(association_name)
          deprecated_remove_association_relation(association_name)
          deprecated_has_collection_method(association_name)
          deprecated_find_in_collection_method(association_name)
          deprecated_find_all_in_collection_method(association_name)
          deprecated_collection_create_method(association_name)
          deprecated_collection_build_method(association_name)
        end

        def create_has_many_reflection(association_id, options, &extension)
          options.assert_valid_keys(
            :class_name, :table_name, :foreign_key,
            :exclusively_dependent, :dependent,
            :select, :conditions, :include, :order, :group, :limit, :offset,
            :as, :through, :source, :source_type,
            :uniq,
            :finder_sql, :counter_sql, 
            :before_add, :after_add, :before_remove, :after_remove, 
            :extend
          )

          options[:extend] = create_extension_module(association_id, extension) if block_given?

          create_reflection(:has_many, association_id, options, self)
        end

        def create_has_one_reflection(association_id, options)
          options.assert_valid_keys(
            :class_name, :foreign_key, :remote, :conditions, :order, :include, :dependent, :counter_cache, :extend, :as
          )

          create_reflection(:has_one, association_id, options, self)
        end

        def create_belongs_to_reflection(association_id, options)
          options.assert_valid_keys(
            :class_name, :foreign_key, :foreign_type, :remote, :conditions, :order, :include, :dependent, 
            :counter_cache, :extend, :polymorphic
          )
          
          reflection = create_reflection(:belongs_to, association_id, options, self)

          if options[:polymorphic]
            reflection.options[:foreign_type] ||= reflection.class_name.underscore + "_type"
          end

          reflection
        end
        
        def create_has_and_belongs_to_many_reflection(association_id, options, &extension)
          options.assert_valid_keys(
            :class_name, :table_name, :join_table, :foreign_key, :association_foreign_key, 
            :select, :conditions, :include, :order, :group, :limit, :offset,
            :uniq, 
            :finder_sql, :delete_sql, :insert_sql,
            :before_add, :after_add, :before_remove, :after_remove, 
            :extend
          )

          options[:extend] = create_extension_module(association_id, extension) if block_given?

          reflection = create_reflection(:has_and_belongs_to_many, association_id, options, self)

          reflection.options[:join_table] ||= join_table_name(undecorated_table_name(self.to_s), undecorated_table_name(reflection.class_name))
          
          reflection
        end

        def reflect_on_included_associations(associations)
          [ associations ].flatten.collect { |association| reflect_on_association(association.to_s.intern) }
        end

        def guard_against_unlimitable_reflections(reflections, options)
          if (options[:offset] || options[:limit]) && !using_limitable_reflections?(reflections)
            raise(
              ConfigurationError, 
              "You can not use offset and limit together with has_many or has_and_belongs_to_many associations"
            )
          end
        end

        def select_all_rows(options, join_dependency)
          connection.select_all(
            construct_finder_sql_with_included_associations(options, join_dependency),
            "#{name} Load Including Associations"
          )
        end

        def construct_finder_sql_with_included_associations(options, join_dependency)
          scope = scope(:find)
          sql = "SELECT #{column_aliases(join_dependency)} FROM #{(scope && scope[:from]) || options[:from] || table_name} "
          sql << join_dependency.join_associations.collect{|join| join.association_join }.join
 
          add_joins!(sql, options, scope)
          add_conditions!(sql, options[:conditions], scope)
          add_limited_ids_condition!(sql, options, join_dependency) if !using_limitable_reflections?(join_dependency.reflections) && ((scope && scope[:limit]) || options[:limit])

          sql << "GROUP BY #{options[:group]} " if options[:group]
 
          add_order!(sql, options[:order], scope)
          add_limit!(sql, options, scope) if using_limitable_reflections?(join_dependency.reflections)
          add_lock!(sql, options, scope)
 
          return sanitize_sql(sql)
        end
 
        def add_limited_ids_condition!(sql, options, join_dependency)
          unless (id_list = select_limited_ids_list(options, join_dependency)).empty?
            sql << "#{condition_word(sql)} #{table_name}.#{primary_key} IN (#{id_list}) "
          else
            throw :invalid_query
          end
        end
 
        def select_limited_ids_list(options, join_dependency)
          connection.select_all(
            construct_finder_sql_for_association_limiting(options, join_dependency),
            "#{name} Load IDs For Limited Eager Loading"
          ).collect { |row| connection.quote(row[primary_key]) }.join(", ")
        end

        def construct_finder_sql_for_association_limiting(options, join_dependency)
          scope       = scope(:find)
          is_distinct = include_eager_conditions?(options) || include_eager_order?(options)
          sql = "SELECT "
          if is_distinct
            sql << connection.distinct("#{table_name}.#{primary_key}", options[:order])
          else
            sql << primary_key
          end
          sql << " FROM #{table_name} "

          if is_distinct
            sql << join_dependency.join_associations.collect(&:association_join).join
            add_joins!(sql, options, scope)
          end

          add_conditions!(sql, options[:conditions], scope)
          if options[:order]
            if is_distinct
              connection.add_order_by_for_association_limiting!(sql, options)
            else
              sql << "ORDER BY #{options[:order]}"
            end
          end
          add_limit!(sql, options, scope)
          return sanitize_sql(sql)
        end

        # Checks if the conditions reference a table other than the current model table
        def include_eager_conditions?(options)
          # look in both sets of conditions
          conditions = [scope(:find, :conditions), options[:conditions]].inject([]) do |all, cond|
            case cond
              when nil   then all
              when Array then all << cond.first
              else            all << cond
            end
          end
          return false unless conditions.any?
          conditions.join(' ').scan(/([\.\w]+)\.\w+/).flatten.any? do |condition_table_name|
            condition_table_name != table_name
          end
        end
        
        # Checks if the query order references a table other than the current model's table.
        def include_eager_order?(options)
          order = options[:order]
          return false unless order
          order.scan(/([\.\w]+)\.\w+/).flatten.any? do |order_table_name|
            order_table_name != table_name
          end
        end

        def using_limitable_reflections?(reflections)
          reflections.reject { |r| [ :belongs_to, :has_one ].include?(r.macro) }.length.zero?
        end

        def column_aliases(join_dependency)
          join_dependency.joins.collect{|join| join.column_names_with_alias.collect{|column_name, aliased_name|
              "#{join.aliased_table_name}.#{connection.quote_column_name column_name} AS #{aliased_name}"}}.flatten.join(", ")
        end

        def add_association_callbacks(association_name, options)
          callbacks = %w(before_add after_add before_remove after_remove)
          callbacks.each do |callback_name|
            full_callback_name = "#{callback_name}_for_#{association_name}"
            defined_callbacks = options[callback_name.to_sym]
            if options.has_key?(callback_name.to_sym)
              class_inheritable_reader full_callback_name.to_sym
              write_inheritable_array(full_callback_name.to_sym, [defined_callbacks].flatten)
            end
          end
        end

        def condition_word(sql)
          sql =~ /where/i ? " AND " : "WHERE "
        end

        def create_extension_module(association_id, extension)
          extension_module_name = "#{self.to_s}#{association_id.to_s.camelize}AssociationExtension"

          silence_warnings do
            Object.const_set(extension_module_name, Module.new(&extension))
          end
          
          extension_module_name.constantize
        end

        class JoinDependency # :nodoc:
          attr_reader :joins, :reflections, :table_aliases

          def initialize(base, associations, joins)
            @joins                 = [JoinBase.new(base, joins)]
            @associations          = associations
            @reflections           = []
            @base_records_hash     = {}
            @base_records_in_order = []
            @table_aliases         = Hash.new { |aliases, table| aliases[table] = 0 }
            @table_aliases[base.table_name] = 1
            build(associations)
          end

          def join_associations
            @joins[1..-1].to_a
          end

          def join_base
            @joins[0]
          end

          def instantiate(rows)
            rows.each_with_index do |row, i|
              primary_id = join_base.record_id(row)
              unless @base_records_hash[primary_id]
                @base_records_in_order << (@base_records_hash[primary_id] = join_base.instantiate(row))
              end
              construct(@base_records_hash[primary_id], @associations, join_associations.dup, row)
            end
            return @base_records_in_order
          end

          def aliased_table_names_for(table_name)
            joins.select{|join| join.table_name == table_name }.collect{|join| join.aliased_table_name}
          end

          protected
            def build(associations, parent = nil)
              parent ||= @joins.last
              case associations
                when Symbol, String
                  reflection = parent.reflections[associations.to_s.intern] or
                  raise ConfigurationError, "Association named '#{ associations }' was not found; perhaps you misspelled it?"
                  @reflections << reflection
                  @joins << JoinAssociation.new(reflection, self, parent)
                when Array
                  associations.each do |association|
                    build(association, parent)
                  end
                when Hash
                  associations.keys.sort{|a,b|a.to_s<=>b.to_s}.each do |name|
                    build(name, parent)
                    build(associations[name])
                  end
                else
                  raise ConfigurationError, associations.inspect
              end
            end

            def construct(parent, associations, joins, row)
              case associations
                when Symbol, String
                  while (join = joins.shift).reflection.name.to_s != associations.to_s
                    raise ConfigurationError, "Not Enough Associations" if joins.empty?
                  end
                  construct_association(parent, join, row)
                when Array
                  associations.each do |association|
                    construct(parent, association, joins, row)
                  end
                when Hash
                  associations.keys.sort{|a,b|a.to_s<=>b.to_s}.each do |name|
                    association = construct_association(parent, joins.shift, row)
                    construct(association, associations[name], joins, row) if association
                  end
                else
                  raise ConfigurationError, associations.inspect
              end
            end

            def construct_association(record, join, row)
              case join.reflection.macro
                when :has_many, :has_and_belongs_to_many
                  collection = record.send(join.reflection.name)
                  collection.loaded

                  return nil if record.id.to_s != join.parent.record_id(row).to_s or row[join.aliased_primary_key].nil?
                  association = join.instantiate(row)
                  collection.target.push(association) unless collection.target.include?(association)
                when :has_one
                  return if record.id.to_s != join.parent.record_id(row).to_s
                  association = join.instantiate(row) unless row[join.aliased_primary_key].nil?
                  record.send("set_#{join.reflection.name}_target", association)
                when :belongs_to
                  return if record.id.to_s != join.parent.record_id(row).to_s or row[join.aliased_primary_key].nil?
                  association = join.instantiate(row)
                  record.send("set_#{join.reflection.name}_target", association)
                else
                  raise ConfigurationError, "unknown macro: #{join.reflection.macro}"
              end
              return association
            end

          class JoinBase # :nodoc:
            attr_reader :active_record, :table_joins
            delegate    :table_name, :column_names, :primary_key, :reflections, :sanitize_sql, :to => :active_record

            def initialize(active_record, joins = nil)
              @active_record = active_record
              @cached_record = {}
              @table_joins   = joins
            end

            def aliased_prefix
              "t0"
            end

            def aliased_primary_key
              "#{ aliased_prefix }_r0"
            end

            def aliased_table_name
              active_record.table_name
            end

            def column_names_with_alias
              unless @column_names_with_alias
                @column_names_with_alias = []
                ([primary_key] + (column_names - [primary_key])).each_with_index do |column_name, i|
                  @column_names_with_alias << [column_name, "#{ aliased_prefix }_r#{ i }"]
                end
              end
              return @column_names_with_alias
            end

            def extract_record(row)
              column_names_with_alias.inject({}){|record, (cn, an)| record[cn] = row[an]; record}
            end

            def record_id(row)
              row[aliased_primary_key]
            end

            def instantiate(row)
              @cached_record[record_id(row)] ||= active_record.send(:instantiate, extract_record(row))
            end
          end

          class JoinAssociation < JoinBase # :nodoc:
            attr_reader :reflection, :parent, :aliased_table_name, :aliased_prefix, :aliased_join_table_name, :parent_table_name
            delegate    :options, :klass, :through_reflection, :source_reflection, :to => :reflection

            def initialize(reflection, join_dependency, parent = nil)
              reflection.check_validity!
              if reflection.options[:polymorphic]
                raise EagerLoadPolymorphicError.new(reflection)
              end

              super(reflection.klass)
              @parent             = parent
              @reflection         = reflection
              @aliased_prefix     = "t#{ join_dependency.joins.size }"
              @aliased_table_name = table_name #.tr('.', '_') # start with the table name, sub out any .'s
              @parent_table_name  = parent.active_record.table_name

              if !parent.table_joins.blank? && parent.table_joins.to_s.downcase =~ %r{join(\s+\w+)?\s+#{aliased_table_name.downcase}\son}
                join_dependency.table_aliases[aliased_table_name] += 1
              end
              
              unless join_dependency.table_aliases[aliased_table_name].zero?
                # if the table name has been used, then use an alias
                @aliased_table_name = active_record.connection.table_alias_for "#{pluralize(reflection.name)}_#{parent_table_name}"
                table_index = join_dependency.table_aliases[aliased_table_name]
                join_dependency.table_aliases[aliased_table_name] += 1
                @aliased_table_name = @aliased_table_name[0..active_record.connection.table_alias_length-3] + "_#{table_index+1}" if table_index > 0
              else
                join_dependency.table_aliases[aliased_table_name] += 1
              end
              
              if reflection.macro == :has_and_belongs_to_many || (reflection.macro == :has_many && reflection.options[:through])
                @aliased_join_table_name = reflection.macro == :has_and_belongs_to_many ? reflection.options[:join_table] : reflection.through_reflection.klass.table_name
                unless join_dependency.table_aliases[aliased_join_table_name].zero?
                  @aliased_join_table_name = active_record.connection.table_alias_for "#{pluralize(reflection.name)}_#{parent_table_name}_join"
                  table_index = join_dependency.table_aliases[aliased_join_table_name]
                  join_dependency.table_aliases[aliased_join_table_name] += 1
                  @aliased_join_table_name = @aliased_join_table_name[0..active_record.connection.table_alias_length-3] + "_#{table_index+1}" if table_index > 0
                else
                  join_dependency.table_aliases[aliased_join_table_name] += 1
                end
              end
            end

            def association_join
              join = case reflection.macro
                when :has_and_belongs_to_many
                  " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [
                     table_alias_for(options[:join_table], aliased_join_table_name),
                     aliased_join_table_name,
                     options[:foreign_key] || reflection.active_record.to_s.foreign_key,
                     parent.aliased_table_name, reflection.active_record.primary_key] +
                  " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [
                     table_name_and_alias, aliased_table_name, klass.primary_key,
                     aliased_join_table_name, options[:association_foreign_key] || klass.to_s.foreign_key
                     ]
                when :has_many, :has_one
                  case
                    when reflection.macro == :has_many && reflection.options[:through]
                      through_conditions = through_reflection.options[:conditions] ? "AND #{interpolate_sql(sanitize_sql(through_reflection.options[:conditions]))}" : ''
                      
                      jt_foreign_key = jt_as_extra = jt_source_extra = jt_sti_extra = nil 
                      first_key = second_key = as_extra = nil 
                      
                      if through_reflection.options[:as] # has_many :through against a polymorphic join
                        jt_foreign_key = through_reflection.options[:as].to_s + '_id'
                        jt_as_extra = " AND %s.%s = %s" % [
                          aliased_join_table_name,
                          reflection.active_record.connection.quote_column_name(through_reflection.options[:as].to_s + '_type'),
                          klass.quote_value(parent.active_record.base_class.name)
                        ]
                      else
                        jt_foreign_key = through_reflection.primary_key_name 
                      end
                        
                      case source_reflection.macro
                      when :has_many
                        if source_reflection.options[:as] 
                          first_key   = "#{source_reflection.options[:as]}_id" 
                          second_key  = options[:foreign_key] || primary_key 
                          as_extra    = " AND %s.%s = %s" % [
                            aliased_table_name,
                            reflection.active_record.connection.quote_column_name("#{source_reflection.options[:as]}_type"),  
                            klass.quote_value(source_reflection.active_record.base_class.name) 
                          ]
                        else
                          first_key   = through_reflection.klass.base_class.to_s.foreign_key
                          second_key  = options[:foreign_key] || primary_key
                        end
                        
                        unless through_reflection.klass.descends_from_active_record?
                          jt_sti_extra = " AND %s.%s = %s" % [
                            aliased_join_table_name,
                            reflection.active_record.connection.quote_column_name(through_reflection.active_record.inheritance_column),
                            through_reflection.klass.quote_value(through_reflection.klass.name.demodulize)]
                        end
                      when :belongs_to
                        first_key = primary_key
                        if reflection.options[:source_type]
                          second_key = source_reflection.association_foreign_key
                          jt_source_extra = " AND %s.%s = %s" % [
                            aliased_join_table_name,
                            reflection.active_record.connection.quote_column_name(reflection.source_reflection.options[:foreign_type]),
                            klass.quote_value(reflection.options[:source_type])
                          ]
                        else
                          second_key = source_reflection.options[:foreign_key] || klass.to_s.foreign_key
                        end
                      end

                      " LEFT OUTER JOIN %s ON (%s.%s = %s.%s%s%s%s) " % [
                        table_alias_for(through_reflection.klass.table_name, aliased_join_table_name),
                        parent.aliased_table_name, reflection.active_record.connection.quote_column_name(parent.primary_key),
                        aliased_join_table_name, reflection.active_record.connection.quote_column_name(jt_foreign_key), 
                        jt_as_extra, jt_source_extra, jt_sti_extra
                      ] +
                      " LEFT OUTER JOIN %s ON (%s.%s = %s.%s%s) " % [
                        table_name_and_alias, 
                        aliased_table_name, reflection.active_record.connection.quote_column_name(first_key),
                        aliased_join_table_name, reflection.active_record.connection.quote_column_name(second_key),
                        as_extra
                      ]

                    when reflection.macro == :has_many && reflection.options[:as]
                      " LEFT OUTER JOIN %s ON %s.%s = %s.%s AND %s.%s = %s" % [
                        table_name_and_alias,
                        aliased_table_name, "#{reflection.options[:as]}_id",
                        parent.aliased_table_name, parent.primary_key,
                        aliased_table_name, "#{reflection.options[:as]}_type",
                        klass.quote_value(parent.active_record.base_class.name)
                      ]
                    when reflection.macro == :has_one && reflection.options[:as]
                      " LEFT OUTER JOIN %s ON %s.%s = %s.%s AND %s.%s = %s " % [
                        table_name_and_alias,
                        aliased_table_name, "#{reflection.options[:as]}_id",
                        parent.aliased_table_name, parent.primary_key,
                        aliased_table_name, "#{reflection.options[:as]}_type",
                        klass.quote_value(reflection.active_record.base_class.name)
                      ]
                    else
                      foreign_key = options[:foreign_key] || reflection.active_record.name.foreign_key
                      " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [
                        table_name_and_alias,
                        aliased_table_name, foreign_key,
                        parent.aliased_table_name, parent.primary_key
                      ]
                  end
                when :belongs_to
                  " LEFT OUTER JOIN %s ON %s.%s = %s.%s " % [
                     table_name_and_alias, aliased_table_name, reflection.klass.primary_key,
                     parent.aliased_table_name, options[:foreign_key] || klass.to_s.foreign_key
                    ]
                else
                  ""
              end || ''
              join << %(AND %s.%s = %s ) % [
                aliased_table_name, 
                reflection.active_record.connection.quote_column_name(klass.inheritance_column), 
                klass.quote_value(klass.name.demodulize)] unless klass.descends_from_active_record?

              [through_reflection, reflection].each do |ref|
                join << "AND #{interpolate_sql(sanitize_sql(ref.options[:conditions]))} " if ref && ref.options[:conditions]
              end

              join
            end
            
            protected

              def pluralize(table_name)
                ActiveRecord::Base.pluralize_table_names ? table_name.to_s.pluralize : table_name
              end
              
              def table_alias_for(table_name, table_alias)
                "#{table_name} #{table_alias if table_name != table_alias}".strip
              end

              def table_name_and_alias
                table_alias_for table_name, @aliased_table_name
              end

              def interpolate_sql(sql)
                instance_eval("%@#{sql.gsub('@', '\@')}@") 
              end 
          end
        end
    end
  end
end