aboutsummaryrefslogtreecommitdiffstats
path: root/activeresource/lib/active_resource/base.rb
blob: 6cb5beb7898d7f8ced4d187254f8ac2c6eca96e0 (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
require 'active_resource/connection'
require 'cgi'
require 'set'

module ActiveResource
  # ActiveResource::Base is the main class for mapping RESTful resources as models in a Rails application.
  #
  # For an outline of what Active Resource is capable of, see link:files/vendor/rails/activeresource/README.html.
  #
  # == Automated mapping
  #
  # Active Resource objects represent your RESTful resources as manipulatable Ruby objects.  To map resources
  # to Ruby objects, Active Resource only needs a class name that corresponds to the resource name (e.g., the class
  # Person maps to the resources people, very similarly to Active Record) and a +site+ value, which holds the
  # URI of the resources.
  #
  #   class Person < ActiveResource::Base
  #     self.site = "http://api.people.com:3000/"
  #   end
  #
  # Now the Person class is mapped to RESTful resources located at <tt>http://api.people.com:3000/people/</tt>, and
  # you can now use Active Resource's lifecycle methods to manipulate resources. In the case where you already have
  # an existing model with the same name as the desired RESTful resource you can set the +element_name+ value.
  #
  #   class PersonResource < ActiveResource::Base
  #     self.site = "http://api.people.com:3000/"
  #     self.element_name = "person"
  #   end
  #
  #
  # == Lifecycle methods
  #
  # Active Resource exposes methods for creating, finding, updating, and deleting resources
  # from REST web services.
  #
  #   ryan = Person.new(:first => 'Ryan', :last => 'Daigle')
  #   ryan.save                # => true
  #   ryan.id                  # => 2
  #   Person.exists?(ryan.id)  # => true
  #   ryan.exists?             # => true
  #
  #   ryan = Person.find(1)
  #   # Resource holding our newly created Person object
  #
  #   ryan.first = 'Rizzle'
  #   ryan.save                # => true
  #
  #   ryan.destroy             # => true
  #
  # As you can see, these are very similar to Active Record's lifecycle methods for database records.
  # You can read more about each of these methods in their respective documentation.
  #
  # === Custom REST methods
  #
  # Since simple CRUD/lifecycle methods can't accomplish every task, Active Resource also supports
  # defining your own custom REST methods. To invoke them, Active Resource provides the <tt>get</tt>,
  # <tt>post</tt>, <tt>put</tt> and <tt>\delete</tt> methods where you can specify a custom REST method
  # name to invoke.
  #
  #   # POST to the custom 'register' REST method, i.e. POST /people/new/register.xml.
  #   Person.new(:name => 'Ryan').post(:register)
  #   # => { :id => 1, :name => 'Ryan', :position => 'Clerk' }
  #
  #   # PUT an update by invoking the 'promote' REST method, i.e. PUT /people/1/promote.xml?position=Manager.
  #   Person.find(1).put(:promote, :position => 'Manager')
  #   # => { :id => 1, :name => 'Ryan', :position => 'Manager' }
  #
  #   # GET all the positions available, i.e. GET /people/positions.xml.
  #   Person.get(:positions)
  #   # => [{:name => 'Manager'}, {:name => 'Clerk'}]
  #
  #   # DELETE to 'fire' a person, i.e. DELETE /people/1/fire.xml.
  #   Person.find(1).delete(:fire)
  #
  # For more information on using custom REST methods, see the
  # ActiveResource::CustomMethods documentation.
  #
  # == Validations
  #
  # You can validate resources client side by overriding validation methods in the base class.
  #
  #   class Person < ActiveResource::Base
  #      self.site = "http://api.people.com:3000/"
  #      protected
  #        def validate
  #          errors.add("last", "has invalid characters") unless last =~ /[a-zA-Z]*/
  #        end
  #   end
  #
  # See the ActiveResource::Validations documentation for more information.
  #
  # == Authentication
  #
  # Many REST APIs will require authentication, usually in the form of basic
  # HTTP authentication.  Authentication can be specified by:
  # * putting the credentials in the URL for the +site+ variable.
  #
  #    class Person < ActiveResource::Base
  #      self.site = "http://ryan:password@api.people.com:3000/"
  #    end
  #
  # * defining +user+ and/or +password+ variables
  #
  #    class Person < ActiveResource::Base
  #      self.site = "http://api.people.com:3000/"
  #      self.user = "ryan"
  #      self.password = "password"
  #    end
  #
  # For obvious security reasons, it is probably best if such services are available
  # over HTTPS.
  #
  # Note: Some values cannot be provided in the URL passed to site.  e.g. email addresses
  # as usernames.  In those situations you should use the separate user and password option.
  #
  # == Errors & Validation
  #
  # Error handling and validation is handled in much the same manner as you're used to seeing in
  # Active Record.  Both the response code in the HTTP response and the body of the response are used to
  # indicate that an error occurred.
  #
  # === Resource errors
  #
  # When a GET is requested for a resource that does not exist, the HTTP <tt>404</tt> (Resource Not Found)
  # response code will be returned from the server which will raise an ActiveResource::ResourceNotFound
  # exception.
  #
  #   # GET http://api.people.com:3000/people/999.xml
  #   ryan = Person.find(999) # 404, raises ActiveResource::ResourceNotFound
  #
  # <tt>404</tt> is just one of the HTTP error response codes that Active Resource will handle with its own exception. The
  # following HTTP response codes will also result in these exceptions:
  # 
  # * 200..399 - Valid response, no exception (other than 301, 302)
  # * 301, 302 - ActiveResource::Redirection
  # * 400 - ActiveResource::BadRequest
  # * 401 - ActiveResource::UnauthorizedAccess
  # * 403 - ActiveResource::ForbiddenAccess
  # * 404 - ActiveResource::ResourceNotFound
  # * 405 - ActiveResource::MethodNotAllowed
  # * 409 - ActiveResource::ResourceConflict
  # * 422 - ActiveResource::ResourceInvalid (rescued by save as validation errors)
  # * 401..499 - ActiveResource::ClientError
  # * 500..599 - ActiveResource::ServerError
  # * Other - ActiveResource::ConnectionError
  #
  # These custom exceptions allow you to deal with resource errors more naturally and with more precision
  # rather than returning a general HTTP error.  For example:
  #
  #   begin
  #     ryan = Person.find(my_id)
  #   rescue ActiveResource::ResourceNotFound
  #     redirect_to :action => 'not_found'
  #   rescue ActiveResource::ResourceConflict, ActiveResource::ResourceInvalid
  #     redirect_to :action => 'new'
  #   end
  #
  # === Validation errors
  #
  # Active Resource supports validations on resources and will return errors if any of these validations fail
  # (e.g., "First name can not be blank" and so on).  These types of errors are denoted in the response by
  # a response code of <tt>422</tt> and an XML representation of the validation errors.  The save operation will
  # then fail (with a <tt>false</tt> return value) and the validation errors can be accessed on the resource in question.
  #
  #   ryan = Person.find(1)
  #   ryan.first # => ''
  #   ryan.save  # => false
  #
  #   # When
  #   # PUT http://api.people.com:3000/people/1.xml
  #   # is requested with invalid values, the response is:
  #   #
  #   # Response (422):
  #   # <errors type="array"><error>First cannot be empty</error></errors>
  #   #
  #
  #   ryan.errors.invalid?(:first)  # => true
  #   ryan.errors.full_messages     # => ['First cannot be empty']
  #
  # Learn more about Active Resource's validation features in the ActiveResource::Validations documentation.
  #
  # === Timeouts
  #
  # Active Resource relies on HTTP to access RESTful APIs and as such is inherently susceptible to slow or
  # unresponsive servers. In such cases, your Active Resource method calls could \timeout. You can control the
  # amount of time before Active Resource times out with the +timeout+ variable.
  #
  #   class Person < ActiveResource::Base
  #     self.site = "http://api.people.com:3000/"
  #     self.timeout = 5
  #   end
  #
  # This sets the +timeout+ to 5 seconds. You can adjust the +timeout+ to a value suitable for the RESTful API
  # you are accessing. It is recommended to set this to a reasonably low value to allow your Active Resource
  # clients (especially if you are using Active Resource in a Rails application) to fail-fast (see
  # http://en.wikipedia.org/wiki/Fail-fast) rather than cause cascading failures that could incapacitate your
  # server.
  #
  # When a \timeout occurs, an ActiveResource::TimeoutError is raised. You should rescue from
  # ActiveResource::TimeoutError in your Active Resource method calls.
  #
  # Internally, Active Resource relies on Ruby's Net::HTTP library to make HTTP requests. Setting +timeout+
  # sets the <tt>read_timeout</tt> of the internal Net::HTTP instance to the same value. The default
  # <tt>read_timeout</tt> is 60 seconds on most Ruby implementations.
  class Base
    ##
    # :singleton-method:
    # The logger for diagnosing and tracing Active Resource calls.
    cattr_accessor :logger

    class << self
      # Gets the URI of the REST resources to map for this class.  The site variable is required for
      # Active Resource's mapping to work.
      def site
        # Not using superclass_delegating_reader because don't want subclasses to modify superclass instance
        #
        # With superclass_delegating_reader
        #
        #   Parent.site = 'http://anonymous@test.com'
        #   Subclass.site # => 'http://anonymous@test.com'
        #   Subclass.site.user = 'david'
        #   Parent.site # => 'http://david@test.com'
        #
        # Without superclass_delegating_reader (expected behaviour)
        #
        #   Parent.site = 'http://anonymous@test.com'
        #   Subclass.site # => 'http://anonymous@test.com'
        #   Subclass.site.user = 'david' # => TypeError: can't modify frozen object
        #
        if defined?(@site)
          @site
        elsif superclass != Object && superclass.site
          superclass.site.dup.freeze
        end
      end

      # Sets the URI of the REST resources to map for this class to the value in the +site+ argument.
      # The site variable is required for Active Resource's mapping to work.
      def site=(site)
        @connection = nil
        if site.nil?
          @site = nil
        else
          @site = create_site_uri_from(site)
          @user = URI.decode(@site.user) if @site.user
          @password = URI.decode(@site.password) if @site.password
        end
      end

      # Gets the \user for REST HTTP authentication.
      def user
        # Not using superclass_delegating_reader. See +site+ for explanation
        if defined?(@user)
          @user
        elsif superclass != Object && superclass.user
          superclass.user.dup.freeze
        end
      end

      # Sets the \user for REST HTTP authentication.
      def user=(user)
        @connection = nil
        @user = user
      end

      # Gets the \password for REST HTTP authentication.
      def password
        # Not using superclass_delegating_reader. See +site+ for explanation
        if defined?(@password)
          @password
        elsif superclass != Object && superclass.password
          superclass.password.dup.freeze
        end
      end

      # Sets the \password for REST HTTP authentication.
      def password=(password)
        @connection = nil
        @password = password
      end

      # Sets the format that attributes are sent and received in from a mime type reference:
      #
      #   Person.format = :json
      #   Person.find(1) # => GET /people/1.json
      #
      #   Person.format = ActiveResource::Formats::XmlFormat
      #   Person.find(1) # => GET /people/1.xml
      #
      # Default format is <tt>:xml</tt>.
      def format=(mime_type_reference_or_format)
        format = mime_type_reference_or_format.is_a?(Symbol) ?
          ActiveResource::Formats[mime_type_reference_or_format] : mime_type_reference_or_format

        write_inheritable_attribute(:format, format)
        connection.format = format if site
      end

      # Returns the current format, default is ActiveResource::Formats::XmlFormat.
      def format
        read_inheritable_attribute(:format) || ActiveResource::Formats[:xml]
      end

      # Sets the number of seconds after which requests to the REST API should time out.
      def timeout=(timeout)
        @connection = nil
        @timeout = timeout
      end

      # Gets the number of seconds after which requests to the REST API should time out.
      def timeout
        if defined?(@timeout)
          @timeout
        elsif superclass != Object && superclass.timeout
          superclass.timeout
        end
      end

      # An instance of ActiveResource::Connection that is the base \connection to the remote service.
      # The +refresh+ parameter toggles whether or not the \connection is refreshed at every request
      # or not (defaults to <tt>false</tt>).
      def connection(refresh = false)
        if defined?(@connection) || superclass == Object
          @connection = Connection.new(site, format) if refresh || @connection.nil?
          @connection.user = user if user
          @connection.password = password if password
          @connection.timeout = timeout if timeout
          @connection
        else
          superclass.connection
        end
      end

      def headers
        @headers ||= {}
      end

      # Do not include any modules in the default element name. This makes it easier to seclude ARes objects
      # in a separate namespace without having to set element_name repeatedly.
      attr_accessor_with_default(:element_name)    { to_s.split("::").last.underscore } #:nodoc:

      attr_accessor_with_default(:collection_name) { element_name.pluralize } #:nodoc:
      attr_accessor_with_default(:primary_key, 'id') #:nodoc:
      
      # Gets the \prefix for a resource's nested URL (e.g., <tt>prefix/collectionname/1.xml</tt>)
      # This method is regenerated at runtime based on what the \prefix is set to.
      def prefix(options={})
        default = site.path
        default << '/' unless default[-1..-1] == '/'
        # generate the actual method based on the current site path
        self.prefix = default
        prefix(options)
      end

      # An attribute reader for the source string for the resource path \prefix.  This
      # method is regenerated at runtime based on what the \prefix is set to.
      def prefix_source
        prefix # generate #prefix and #prefix_source methods first
        prefix_source
      end

      # Sets the \prefix for a resource's nested URL (e.g., <tt>prefix/collectionname/1.xml</tt>).
      # Default value is <tt>site.path</tt>.
      def prefix=(value = '/')
        # Replace :placeholders with '#{embedded options[:lookups]}'
        prefix_call = value.gsub(/:\w+/) { |key| "\#{options[#{key}]}" }

        # Clear prefix parameters in case they have been cached
        @prefix_parameters = nil

        # Redefine the new methods.
        code = <<-end_code
          def prefix_source() "#{value}" end
          def prefix(options={}) "#{prefix_call}" end
        end_code
        silence_warnings { instance_eval code, __FILE__, __LINE__ }
      rescue
        logger.error "Couldn't set prefix: #{$!}\n  #{code}"
        raise
      end

      alias_method :set_prefix, :prefix=  #:nodoc:

      alias_method :set_element_name, :element_name=  #:nodoc:
      alias_method :set_collection_name, :collection_name=  #:nodoc:

      # Gets the element path for the given ID in +id+.  If the +query_options+ parameter is omitted, Rails
      # will split from the \prefix options.
      #
      # ==== Options
      # +prefix_options+ - A \hash to add a \prefix to the request for nested URLs (e.g., <tt>:account_id => 19</tt>
      #                    would yield a URL like <tt>/accounts/19/purchases.xml</tt>).
      # +query_options+ - A \hash to add items to the query string for the request.
      #
      # ==== Examples
      #   Post.element_path(1)
      #   # => /posts/1.xml
      #
      #   Comment.element_path(1, :post_id => 5)
      #   # => /posts/5/comments/1.xml
      #
      #   Comment.element_path(1, :post_id => 5, :active => 1)
      #   # => /posts/5/comments/1.xml?active=1
      #
      #   Comment.element_path(1, {:post_id => 5}, {:active => 1})
      #   # => /posts/5/comments/1.xml?active=1
      #
      def element_path(id, prefix_options = {}, query_options = nil)
        prefix_options, query_options = split_options(prefix_options) if query_options.nil?
        "#{prefix(prefix_options)}#{collection_name}/#{id}.#{format.extension}#{query_string(query_options)}"
      end

      # Gets the collection path for the REST resources.  If the +query_options+ parameter is omitted, Rails
      # will split from the +prefix_options+.
      #
      # ==== Options
      # * +prefix_options+ - A hash to add a prefix to the request for nested URLs (e.g., <tt>:account_id => 19</tt>
      #   would yield a URL like <tt>/accounts/19/purchases.xml</tt>).
      # * +query_options+ - A hash to add items to the query string for the request.
      #
      # ==== Examples
      #   Post.collection_path
      #   # => /posts.xml
      #
      #   Comment.collection_path(:post_id => 5)
      #   # => /posts/5/comments.xml
      #
      #   Comment.collection_path(:post_id => 5, :active => 1)
      #   # => /posts/5/comments.xml?active=1
      #
      #   Comment.collection_path({:post_id => 5}, {:active => 1})
      #   # => /posts/5/comments.xml?active=1
      #
      def collection_path(prefix_options = {}, query_options = nil)
        prefix_options, query_options = split_options(prefix_options) if query_options.nil?
        "#{prefix(prefix_options)}#{collection_name}.#{format.extension}#{query_string(query_options)}"
      end

      alias_method :set_primary_key, :primary_key=  #:nodoc:

      # Creates a new resource instance and makes a request to the remote service
      # that it be saved, making it equivalent to the following simultaneous calls:
      #
      #   ryan = Person.new(:first => 'ryan')
      #   ryan.save
      #
      # Returns the newly created resource.  If a failure has occurred an
      # exception will be raised (see <tt>save</tt>).  If the resource is invalid and
      # has not been saved then <tt>valid?</tt> will return <tt>false</tt>,
      # while <tt>new?</tt> will still return <tt>true</tt>.
      #
      # ==== Examples
      #   Person.create(:name => 'Jeremy', :email => 'myname@nospam.com', :enabled => true)
      #   my_person = Person.find(:first)
      #   my_person.email # => myname@nospam.com
      #
      #   dhh = Person.create(:name => 'David', :email => 'dhh@nospam.com', :enabled => true)
      #   dhh.valid? # => true
      #   dhh.new?   # => false
      #
      #   # We'll assume that there's a validation that requires the name attribute
      #   that_guy = Person.create(:name => '', :email => 'thatguy@nospam.com', :enabled => true)
      #   that_guy.valid? # => false
      #   that_guy.new?   # => true
      def create(attributes = {})
        self.new(attributes).tap { |resource| resource.save }
      end

      # Core method for finding resources.  Used similarly to Active Record's +find+ method.
      #
      # ==== Arguments
      # The first argument is considered to be the scope of the query.  That is, how many
      # resources are returned from the request.  It can be one of the following.
      #
      # * <tt>:one</tt> - Returns a single resource.
      # * <tt>:first</tt> - Returns the first resource found.
      # * <tt>:last</tt> - Returns the last resource found.
      # * <tt>:all</tt> - Returns every resource that matches the request.
      #
      # ==== Options
      #
      # * <tt>:from</tt> - Sets the path or custom method that resources will be fetched from.
      # * <tt>:params</tt> - Sets query and \prefix (nested URL) parameters.
      #
      # ==== Examples
      #   Person.find(1)
      #   # => GET /people/1.xml
      #
      #   Person.find(:all)
      #   # => GET /people.xml
      #
      #   Person.find(:all, :params => { :title => "CEO" })
      #   # => GET /people.xml?title=CEO
      #
      #   Person.find(:first, :from => :managers)
      #   # => GET /people/managers.xml
      #
      #   Person.find(:last, :from => :managers)
      #   # => GET /people/managers.xml
      #
      #   Person.find(:all, :from => "/companies/1/people.xml")
      #   # => GET /companies/1/people.xml
      #
      #   Person.find(:one, :from => :leader)
      #   # => GET /people/leader.xml
      #
      #   Person.find(:all, :from => :developers, :params => { :language => 'ruby' })
      #   # => GET /people/developers.xml?language=ruby
      #
      #   Person.find(:one, :from => "/companies/1/manager.xml")
      #   # => GET /companies/1/manager.xml
      #
      #   StreetAddress.find(1, :params => { :person_id => 1 })
      #   # => GET /people/1/street_addresses/1.xml
      def find(*arguments)
        scope   = arguments.slice!(0)
        options = arguments.slice!(0) || {}

        case scope
          when :all   then find_every(options)
          when :first then find_every(options).first
          when :last  then find_every(options).last
          when :one   then find_one(options)
          else             find_single(scope, options)
        end
      end

      # Deletes the resources with the ID in the +id+ parameter.
      #
      # ==== Options
      # All options specify \prefix and query parameters.
      #
      # ==== Examples
      #   Event.delete(2) # sends DELETE /events/2
      #
      #   Event.create(:name => 'Free Concert', :location => 'Community Center')
      #   my_event = Event.find(:first) # let's assume this is event with ID 7
      #   Event.delete(my_event.id) # sends DELETE /events/7
      #
      #   # Let's assume a request to events/5/cancel.xml
      #   Event.delete(params[:id]) # sends DELETE /events/5
      def delete(id, options = {})
        connection.delete(element_path(id, options))
      end

      # Asserts the existence of a resource, returning <tt>true</tt> if the resource is found.
      #
      # ==== Examples
      #   Note.create(:title => 'Hello, world.', :body => 'Nothing more for now...')
      #   Note.exists?(1) # => true
      #
      #   Note.exists(1349) # => false
      def exists?(id, options = {})
        if id
          prefix_options, query_options = split_options(options[:params])
          path = element_path(id, prefix_options, query_options)
          response = connection.head(path, headers)
          response.code.to_i == 200
        end
        # id && !find_single(id, options).nil?
      rescue ActiveResource::ResourceNotFound
        false
      end

      private
        # Find every resource
        def find_every(options)
          case from = options[:from]
          when Symbol
            instantiate_collection(get(from, options[:params]))
          when String
            path = "#{from}#{query_string(options[:params])}"
            instantiate_collection(connection.get(path, headers) || [])
          else
            prefix_options, query_options = split_options(options[:params])
            path = collection_path(prefix_options, query_options)
            instantiate_collection( (connection.get(path, headers) || []), prefix_options )
          end
        end

        # Find a single resource from a one-off URL
        def find_one(options)
          case from = options[:from]
          when Symbol
            instantiate_record(get(from, options[:params]))
          when String
            path = "#{from}#{query_string(options[:params])}"
            instantiate_record(connection.get(path, headers))
          end
        end

        # Find a single resource from the default URL
        def find_single(scope, options)
          prefix_options, query_options = split_options(options[:params])
          path = element_path(scope, prefix_options, query_options)
          instantiate_record(connection.get(path, headers), prefix_options)
        end

        def instantiate_collection(collection, prefix_options = {})
          collection.collect! { |record| instantiate_record(record, prefix_options) }
        end

        def instantiate_record(record, prefix_options = {})
          new(record).tap do |resource|
            resource.prefix_options = prefix_options
          end
        end


        # Accepts a URI and creates the site URI from that.
        def create_site_uri_from(site)
          site.is_a?(URI) ? site.dup : URI.parse(site)
        end

        # contains a set of the current prefix parameters.
        def prefix_parameters
          @prefix_parameters ||= prefix_source.scan(/:\w+/).map { |key| key[1..-1].to_sym }.to_set
        end

        # Builds the query string for the request.
        def query_string(options)
          "?#{options.to_query}" unless options.nil? || options.empty?
        end

        # split an option hash into two hashes, one containing the prefix options,
        # and the other containing the leftovers.
        def split_options(options = {})
          prefix_options, query_options = {}, {}

          (options || {}).each do |key, value|
            next if key.blank?
            (prefix_parameters.include?(key.to_sym) ? prefix_options : query_options)[key.to_sym] = value
          end

          [ prefix_options, query_options ]
        end
    end

    attr_accessor :attributes #:nodoc:
    attr_accessor :prefix_options #:nodoc:

    # Constructor method for \new resources; the optional +attributes+ parameter takes a \hash
    # of attributes for the \new resource.
    #
    # ==== Examples
    #   my_course = Course.new
    #   my_course.name = "Western Civilization"
    #   my_course.lecturer = "Don Trotter"
    #   my_course.save
    #
    #   my_other_course = Course.new(:name => "Philosophy: Reason and Being", :lecturer => "Ralph Cling")
    #   my_other_course.save
    def initialize(attributes = {})
      @attributes     = {}
      @prefix_options = {}
      load(attributes)
    end

    # Returns a \clone of the resource that hasn't been assigned an +id+ yet and
    # is treated as a \new resource.
    #
    #   ryan = Person.find(1)
    #   not_ryan = ryan.clone
    #   not_ryan.new?  # => true
    #
    # Any active resource member attributes will NOT be cloned, though all other
    # attributes are.  This is to prevent the conflict between any +prefix_options+
    # that refer to the original parent resource and the newly cloned parent
    # resource that does not exist.
    #
    #   ryan = Person.find(1)
    #   ryan.address = StreetAddress.find(1, :person_id => ryan.id)
    #   ryan.hash = {:not => "an ARes instance"}
    #
    #   not_ryan = ryan.clone
    #   not_ryan.new?            # => true
    #   not_ryan.address         # => NoMethodError
    #   not_ryan.hash            # => {:not => "an ARes instance"}
    def clone
      # Clone all attributes except the pk and any nested ARes
      cloned = attributes.reject {|k,v| k == self.class.primary_key || v.is_a?(ActiveResource::Base)}.inject({}) do |attrs, (k, v)|
        attrs[k] = v.clone
        attrs
      end
      # Form the new resource - bypass initialize of resource with 'new' as that will call 'load' which
      # attempts to convert hashes into member objects and arrays into collections of objects.  We want
      # the raw objects to be cloned so we bypass load by directly setting the attributes hash.
      resource = self.class.new({})
      resource.prefix_options = self.prefix_options
      resource.send :instance_variable_set, '@attributes', cloned
      resource
    end


    # Returns +true+ if this object hasn't yet been saved, otherwise, returns +false+.
    #
    # ==== Examples
    #   not_new = Computer.create(:brand => 'Apple', :make => 'MacBook', :vendor => 'MacMall')
    #   not_new.new? # => false
    #
    #   is_new = Computer.new(:brand => 'IBM', :make => 'Thinkpad', :vendor => 'IBM')
    #   is_new.new? # => true
    #
    #   is_new.save
    #   is_new.new? # => false
    #
    def new?
      id.nil?
    end
    alias :new_record? :new?

    # Gets the <tt>\id</tt> attribute of the resource.
    def id
      attributes[self.class.primary_key]
    end

    # Sets the <tt>\id</tt> attribute of the resource.
    def id=(id)
      attributes[self.class.primary_key] = id
    end

    # Allows Active Resource objects to be used as parameters in Action Pack URL generation.
    def to_param
      id && id.to_s
    end

    # Test for equality.  Resource are equal if and only if +other+ is the same object or
    # is an instance of the same class, is not <tt>new?</tt>, and has the same +id+.
    #
    # ==== Examples
    #   ryan = Person.create(:name => 'Ryan')
    #   jamie = Person.create(:name => 'Jamie')
    #
    #   ryan == jamie
    #   # => false (Different name attribute and id)
    #
    #   ryan_again = Person.new(:name => 'Ryan')
    #   ryan == ryan_again
    #   # => false (ryan_again is new?)
    #
    #   ryans_clone = Person.create(:name => 'Ryan')
    #   ryan == ryans_clone
    #   # => false (Different id attributes)
    #
    #   ryans_twin = Person.find(ryan.id)
    #   ryan == ryans_twin
    #   # => true
    #
    def ==(other)
      other.equal?(self) || (other.instance_of?(self.class) && other.id == id && other.prefix_options == prefix_options)
    end

    # Tests for equality (delegates to ==).
    def eql?(other)
      self == other
    end

    # Delegates to id in order to allow two resources of the same type and \id to work with something like:
    #   [Person.find(1), Person.find(2)] & [Person.find(1), Person.find(4)] # => [Person.find(1)]
    def hash
      id.hash
    end

    # Duplicates the current resource without saving it.
    #
    # ==== Examples
    #   my_invoice = Invoice.create(:customer => 'That Company')
    #   next_invoice = my_invoice.dup
    #   next_invoice.new? # => true
    #
    #   next_invoice.save
    #   next_invoice == my_invoice # => false (different id attributes)
    #
    #   my_invoice.customer   # => That Company
    #   next_invoice.customer # => That Company
    def dup
      self.class.new.tap do |resource|
        resource.attributes     = @attributes
        resource.prefix_options = @prefix_options
      end
    end

    # Saves (+POST+) or \updates (+PUT+) a resource.  Delegates to +create+ if the object is \new,
    # +update+ if it exists. If the response to the \save includes a body, it will be assumed that this body
    # is XML for the final object as it looked after the \save (which would include attributes like +created_at+
    # that weren't part of the original submit).
    #
    # ==== Examples
    #   my_company = Company.new(:name => 'RoleModel Software', :owner => 'Ken Auer', :size => 2)
    #   my_company.new? # => true
    #   my_company.save # sends POST /companies/ (create)
    #
    #   my_company.new? # => false
    #   my_company.size = 10
    #   my_company.save # sends PUT /companies/1 (update)
    def save
      new? ? create : update
    end

    # Deletes the resource from the remote service.
    #
    # ==== Examples
    #   my_id = 3
    #   my_person = Person.find(my_id)
    #   my_person.destroy
    #   Person.find(my_id) # 404 (Resource Not Found)
    #
    #   new_person = Person.create(:name => 'James')
    #   new_id = new_person.id # => 7
    #   new_person.destroy
    #   Person.find(new_id) # 404 (Resource Not Found)
    def destroy
      connection.delete(element_path, self.class.headers)
    end

    # Evaluates to <tt>true</tt> if this resource is not <tt>new?</tt> and is
    # found on the remote service.  Using this method, you can check for
    # resources that may have been deleted between the object's instantiation
    # and actions on it.
    #
    # ==== Examples
    #   Person.create(:name => 'Theodore Roosevelt')
    #   that_guy = Person.find(:first)
    #   that_guy.exists? # => true
    #
    #   that_lady = Person.new(:name => 'Paul Bean')
    #   that_lady.exists? # => false
    #
    #   guys_id = that_guy.id
    #   Person.delete(guys_id)
    #   that_guy.exists? # => false
    def exists?
      !new? && self.class.exists?(to_param, :params => prefix_options)
    end

    # Converts the resource to an XML string representation.
    #
    # ==== Options
    # The +options+ parameter is handed off to the +to_xml+ method on each
    # attribute, so it has the same options as the +to_xml+ methods in
    # Active Support.
    #
    # * <tt>:indent</tt> - Set the indent level for the XML output (default is +2+).
    # * <tt>:dasherize</tt> - Boolean option to determine whether or not element names should
    #   replace underscores with dashes (default is <tt>false</tt>).
    # * <tt>:skip_instruct</tt> - Toggle skipping the +instruct!+ call on the XML builder
    #   that generates the XML declaration (default is <tt>false</tt>).
    #
    # ==== Examples
    #   my_group = SubsidiaryGroup.find(:first)
    #   my_group.to_xml
    #   # => <?xml version="1.0" encoding="UTF-8"?>
    #   #    <subsidiary_group> [...] </subsidiary_group>
    #
    #   my_group.to_xml(:dasherize => true)
    #   # => <?xml version="1.0" encoding="UTF-8"?>
    #   #    <subsidiary-group> [...] </subsidiary-group>
    #
    #   my_group.to_xml(:skip_instruct => true)
    #   # => <subsidiary_group> [...] </subsidiary_group>
    def to_xml(options={})
      attributes.to_xml({:root => self.class.element_name}.merge(options))
    end

    # Converts the resource to a JSON string representation.
    #
    # ==== Options
    # The +options+ are passed to the +to_json+ method on each
    # attribute, so the same options as the +to_json+ methods in
    # Active Support.
    #
    # * <tt>:only</tt> - Only include the specified attribute or list of
    #   attributes in the serialized output. Attribute names must be specified
    #   as strings.
    # * <tt>:except</tt> - Do not include the specified attribute or list of
    #   attributes in the serialized output. Attribute names must be specified
    #   as strings.
    #
    # ==== Examples
    #   person = Person.new(:first_name => "Jim", :last_name => "Smith")
    #   person.to_json
    #   # => {"first_name": "Jim", "last_name": "Smith"}
    #
    #   person.to_json(:only => ["first_name"])
    #   # => {"first_name": "Jim"}
    #
    #   person.to_json(:except => ["first_name"])
    #   # => {"last_name": "Smith"}
    def to_json(options={})
      attributes.to_json(options)
    end

    # Returns the serialized string representation of the resource in the configured
    # serialization format specified in ActiveResource::Base.format. The options
    # applicable depend on the configured encoding format.
    def encode(options={})
      case self.class.format
        when ActiveResource::Formats[:xml]
          self.class.format.encode(attributes, {:root => self.class.element_name}.merge(options))
        else
          self.class.format.encode(attributes, options)
      end
    end

    # A method to \reload the attributes of this object from the remote web service.
    #
    # ==== Examples
    #   my_branch = Branch.find(:first)
    #   my_branch.name # => "Wislon Raod"
    #
    #   # Another client fixes the typo...
    #
    #   my_branch.name # => "Wislon Raod"
    #   my_branch.reload
    #   my_branch.name # => "Wilson Road"
    def reload
      self.load(self.class.find(to_param, :params => @prefix_options).attributes)
    end

    # A method to manually load attributes from a \hash. Recursively loads collections of
    # resources.  This method is called in +initialize+ and +create+ when a \hash of attributes
    # is provided.
    #
    # ==== Examples
    #   my_attrs = {:name => 'J&J Textiles', :industry => 'Cloth and textiles'}
    #   my_attrs = {:name => 'Marty', :colors => ["red", "green", "blue"]}
    #
    #   the_supplier = Supplier.find(:first)
    #   the_supplier.name # => 'J&M Textiles'
    #   the_supplier.load(my_attrs)
    #   the_supplier.name('J&J Textiles')
    #
    #   # These two calls are the same as Supplier.new(my_attrs)
    #   my_supplier = Supplier.new
    #   my_supplier.load(my_attrs)
    #
    #   # These three calls are the same as Supplier.create(my_attrs)
    #   your_supplier = Supplier.new
    #   your_supplier.load(my_attrs)
    #   your_supplier.save
    def load(attributes)
      raise ArgumentError, "expected an attributes Hash, got #{attributes.inspect}" unless attributes.is_a?(Hash)
      @prefix_options, attributes = split_options(attributes)
      attributes.each do |key, value|
        @attributes[key.to_s] =
          case value
            when Array
              resource = find_or_create_resource_for_collection(key)
              value.map { |attrs| attrs.is_a?(String) ? attrs.dup : resource.new(attrs) }
            when Hash
              resource = find_or_create_resource_for(key)
              resource.new(value)
            else
              value.dup rescue value
          end
      end
      self
    end

    # For checking <tt>respond_to?</tt> without searching the attributes (which is faster).
    alias_method :respond_to_without_attributes?, :respond_to?

    # A method to determine if an object responds to a message (e.g., a method call). In Active Resource, a Person object with a
    # +name+ attribute can answer <tt>true</tt> to <tt>my_person.respond_to?(:name)</tt>, <tt>my_person.respond_to?(:name=)</tt>, and
    # <tt>my_person.respond_to?(:name?)</tt>.
    def respond_to?(method, include_priv = false)
      method_name = method.to_s
      if attributes.nil?
        return super
      elsif attributes.has_key?(method_name)
        return true
      elsif ['?','='].include?(method_name.last) && attributes.has_key?(method_name.first(-1))
        return true
      end
      # super must be called at the end of the method, because the inherited respond_to?
      # would return true for generated readers, even if the attribute wasn't present
      super
    end


    protected
      def connection(refresh = false)
        self.class.connection(refresh)
      end

      # Update the resource on the remote service.
      def update
        connection.put(element_path(prefix_options), encode, self.class.headers).tap do |response|
          load_attributes_from_response(response)
        end
      end

      # Create (i.e., \save to the remote service) the \new resource.
      def create
        connection.post(collection_path, encode, self.class.headers).tap do |response|
          self.id = id_from_response(response)
          load_attributes_from_response(response)
        end
      end

      def load_attributes_from_response(response)
        if response['Content-Length'] != "0" && response.body.strip.size > 0
          load(self.class.format.decode(response.body))
        end
      end

      # Takes a response from a typical create post and pulls the ID out
      def id_from_response(response)
        response['Location'][/\/([^\/]*?)(\.\w+)?$/, 1] if response['Location']
      end

      def element_path(options = nil)
        self.class.element_path(to_param, options || prefix_options)
      end

      def collection_path(options = nil)
        self.class.collection_path(options || prefix_options)
      end

    private
      # Tries to find a resource for a given collection name; if it fails, then the resource is created
      def find_or_create_resource_for_collection(name)
        find_or_create_resource_for(name.to_s.singularize)
      end

      # Tries to find a resource in a non empty list of nested modules
      # Raises a NameError if it was not found in any of the given nested modules
      def find_resource_in_modules(resource_name, module_names)
        receiver = Object
        namespaces = module_names[0, module_names.size-1].map do |module_name|
          receiver = receiver.const_get(module_name)
        end
        if namespace = namespaces.reverse.detect { |ns| ns.const_defined?(resource_name) }
          return namespace.const_get(resource_name)
        else
          raise NameError
        end
      end

      # Tries to find a resource for a given name; if it fails, then the resource is created
      def find_or_create_resource_for(name)
        resource_name = name.to_s.camelize
        ancestors = self.class.name.split("::")
        if ancestors.size > 1
          find_resource_in_modules(resource_name, ancestors)
        else
          self.class.const_get(resource_name)
        end
      rescue NameError
        if self.class.const_defined?(resource_name)
          resource = self.class.const_get(resource_name)
        else
          resource = self.class.const_set(resource_name, Class.new(ActiveResource::Base))
        end
        resource.prefix = self.class.prefix
        resource.site   = self.class.site
        resource
      end

      def split_options(options = {})
        self.class.__send__(:split_options, options)
      end

      def method_missing(method_symbol, *arguments) #:nodoc:
        method_name = method_symbol.to_s

        case method_name.last
          when "="
            attributes[method_name.first(-1)] = arguments.first
          when "?"
            attributes[method_name.first(-1)]
          else
            attributes.has_key?(method_name) ? attributes[method_name] : super
        end
      end
  end
end