aboutsummaryrefslogtreecommitdiffstats
path: root/activerecord/lib/active_record/reflection.rb
blob: 60b73e9fe5fae8452da08555abc4c8291bfd225b (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
require 'active_support/core_ext/class/attribute'
require 'active_support/core_ext/object/inclusion'

module ActiveRecord
  # = Active Record Reflection
  module Reflection # :nodoc:
    extend ActiveSupport::Concern

    included do
      extend ActiveModel::Configuration
      config_attribute :reflections
      self.reflections = {}
    end

    # Reflection enables to interrogate Active Record classes and objects
    # about their associations and aggregations. This information can,
    # for example, be used in a form builder that takes an Active Record object
    # and creates input fields for all of the attributes depending on their type
    # and displays the associations to other objects.
    #
    # MacroReflection class has info for AggregateReflection and AssociationReflection
    # classes.
    module ClassMethods
      def create_reflection(macro, name, options, active_record)
        case macro
          when :has_many, :belongs_to, :has_one, :has_and_belongs_to_many
            klass = options[:through] ? ThroughReflection : AssociationReflection
            reflection = klass.new(macro, name, options, active_record)
          when :composed_of
            reflection = AggregateReflection.new(macro, name, options, active_record)
        end

        self.reflections = self.reflections.merge(name => reflection)
        reflection
      end

      # Returns an array of AggregateReflection objects for all the aggregations in the class.
      def reflect_on_all_aggregations
        reflections.values.grep(AggregateReflection)
      end

      # Returns the AggregateReflection object for the named +aggregation+ (use the symbol).
      #
      #   Account.reflect_on_aggregation(:balance) # => the balance AggregateReflection
      #
      def reflect_on_aggregation(aggregation)
        reflections[aggregation].is_a?(AggregateReflection) ? reflections[aggregation] : nil
      end

      # Returns an array of AssociationReflection objects for all the
      # associations in the class. If you only want to reflect on a certain
      # association type, pass in the symbol (<tt>:has_many</tt>, <tt>:has_one</tt>,
      # <tt>:belongs_to</tt>) as the first parameter.
      #
      # Example:
      #
      #   Account.reflect_on_all_associations             # returns an array of all associations
      #   Account.reflect_on_all_associations(:has_many)  # returns an array of all has_many associations
      #
      def reflect_on_all_associations(macro = nil)
        association_reflections = reflections.values.grep(AssociationReflection)
        macro ? association_reflections.select { |reflection| reflection.macro == macro } : association_reflections
      end

      # Returns the AssociationReflection object for the +association+ (use the symbol).
      #
      #   Account.reflect_on_association(:owner)             # returns the owner AssociationReflection
      #   Invoice.reflect_on_association(:line_items).macro  # returns :has_many
      #
      def reflect_on_association(association)
        reflections[association].is_a?(AssociationReflection) ? reflections[association] : nil
      end

      # Returns an array of AssociationReflection objects for all associations which have <tt>:autosave</tt> enabled.
      def reflect_on_all_autosave_associations
        reflections.values.select { |reflection| reflection.options[:autosave] }
      end
    end


    # Abstract base class for AggregateReflection and AssociationReflection. Objects of
    # AggregateReflection and AssociationReflection are returned by the Reflection::ClassMethods.
    class MacroReflection
      # Returns the name of the macro.
      #
      # <tt>composed_of :balance, :class_name => 'Money'</tt> returns <tt>:balance</tt>
      # <tt>has_many :clients</tt> returns <tt>:clients</tt>
      attr_reader :name

      # Returns the macro type.
      #
      # <tt>composed_of :balance, :class_name => 'Money'</tt> returns <tt>:composed_of</tt>
      # <tt>has_many :clients</tt> returns <tt>:has_many</tt>
      attr_reader :macro

      # Returns the hash of options used for the macro.
      #
      # <tt>composed_of :balance, :class_name => 'Money'</tt> returns <tt>{ :class_name => "Money" }</tt>
      # <tt>has_many :clients</tt> returns +{}+
      attr_reader :options

      attr_reader :active_record

      attr_reader :plural_name # :nodoc:

      def initialize(macro, name, options, active_record)
        @macro         = macro
        @name          = name
        @options       = options
        @active_record = active_record
        @plural_name   = active_record.pluralize_table_names ?
                            name.to_s.pluralize : name.to_s
      end

      # Returns the class for the macro.
      #
      # <tt>composed_of :balance, :class_name => 'Money'</tt> returns the Money class
      # <tt>has_many :clients</tt> returns the Client class
      def klass
        @klass ||= class_name.constantize
      end

      # Returns the class name for the macro.
      #
      # <tt>composed_of :balance, :class_name => 'Money'</tt> returns <tt>'Money'</tt>
      # <tt>has_many :clients</tt> returns <tt>'Client'</tt>
      def class_name
        @class_name ||= (options[:class_name] || derive_class_name).to_s
      end

      # Returns +true+ if +self+ and +other_aggregation+ have the same +name+ attribute, +active_record+ attribute,
      # and +other_aggregation+ has an options hash assigned to it.
      def ==(other_aggregation)
        super ||
          other_aggregation.kind_of?(self.class) &&
          name == other_aggregation.name &&
          other_aggregation.options &&
          active_record == other_aggregation.active_record
      end

      def sanitized_conditions #:nodoc:
        @sanitized_conditions ||= klass.send(:sanitize_sql, options[:conditions]) if options[:conditions]
      end

      private
        def derive_class_name
          name.to_s.camelize
        end
    end


    # Holds all the meta-data about an aggregation as it was specified in the
    # Active Record class.
    class AggregateReflection < MacroReflection #:nodoc:
    end

    # Holds all the meta-data about an association as it was specified in the
    # Active Record class.
    class AssociationReflection < MacroReflection #:nodoc:
      # Returns the target association's class.
      #
      #   class Author < ActiveRecord::Base
      #     has_many :books
      #   end
      #
      #   Author.reflect_on_association(:books).klass
      #   # => Book
      #
      # <b>Note:</b> Do not call +klass.new+ or +klass.create+ to instantiate
      # a new association object. Use +build_association+ or +create_association+
      # instead. This allows plugins to hook into association object creation.
      def klass
        @klass ||= active_record.send(:compute_type, class_name)
      end

      def initialize(macro, name, options, active_record)
        super
        @collection = macro.in?([:has_many, :has_and_belongs_to_many])
      end

      # Returns a new, unsaved instance of the associated class. +options+ will
      # be passed to the class's constructor.
      def build_association(*options, &block)
        klass.new(*options, &block)
      end

      def table_name
        @table_name ||= klass.table_name
      end

      def quoted_table_name
        @quoted_table_name ||= klass.quoted_table_name
      end

      def foreign_key
        @foreign_key ||= options[:foreign_key] || derive_foreign_key
      end

      def foreign_type
        @foreign_type ||= options[:foreign_type] || "#{name}_type"
      end

      def type
        @type ||= options[:as] && "#{options[:as]}_type"
      end

      def primary_key_column
        @primary_key_column ||= klass.columns.find { |c| c.name == klass.primary_key }
      end

      def association_foreign_key
        @association_foreign_key ||= options[:association_foreign_key] || class_name.foreign_key
      end

      # klass option is necessary to support loading polymorphic associations
      def association_primary_key(klass = nil)
        options[:primary_key] || primary_key(klass || self.klass)
      end

      def active_record_primary_key
        @active_record_primary_key ||= options[:primary_key] || primary_key(active_record)
      end

      def counter_cache_column
        if options[:counter_cache] == true
          "#{active_record.name.demodulize.underscore.pluralize}_count"
        elsif options[:counter_cache]
          options[:counter_cache].to_s
        end
      end

      def columns(tbl_name, log_msg)
        @columns ||= klass.connection.columns(tbl_name, log_msg)
      end

      def reset_column_information
        @columns = nil
      end

      def check_validity!
        check_validity_of_inverse!
      end

      def check_validity_of_inverse!
        unless options[:polymorphic]
          if has_inverse? && inverse_of.nil?
            raise InverseOfAssociationNotFoundError.new(self)
          end
        end
      end

      def through_reflection
        nil
      end

      def source_reflection
        nil
      end

      # A chain of reflections from this one back to the owner. For more see the explanation in
      # ThroughReflection.
      def chain
        [self]
      end

      def nested?
        false
      end

      # An array of arrays of conditions. Each item in the outside array corresponds to a reflection
      # in the #chain. The inside arrays are simply conditions (and each condition may itself be
      # a hash, array, arel predicate, etc...)
      def conditions
        [[options[:conditions]].compact]
      end

      alias :source_macro :macro

      def has_inverse?
        @options[:inverse_of]
      end

      def inverse_of
        if has_inverse?
          @inverse_of ||= klass.reflect_on_association(options[:inverse_of])
        end
      end

      def polymorphic_inverse_of(associated_class)
        if has_inverse?
          if inverse_relationship = associated_class.reflect_on_association(options[:inverse_of])
            inverse_relationship
          else
            raise InverseOfAssociationNotFoundError.new(self, associated_class)
          end
        end
      end

      # Returns whether or not this association reflection is for a collection
      # association. Returns +true+ if the +macro+ is either +has_many+ or
      # +has_and_belongs_to_many+, +false+ otherwise.
      def collection?
        @collection
      end

      # Returns whether or not the association should be validated as part of
      # the parent's validation.
      #
      # Unless you explicitly disable validation with
      # <tt>:validate => false</tt>, validation will take place when:
      #
      # * you explicitly enable validation; <tt>:validate => true</tt>
      # * you use autosave; <tt>:autosave => true</tt>
      # * the association is a +has_many+ association
      def validate?
        !options[:validate].nil? ? options[:validate] : (options[:autosave] == true || macro == :has_many)
      end

      # Returns +true+ if +self+ is a +belongs_to+ reflection.
      def belongs_to?
        macro == :belongs_to
      end

      def association_class
        case macro
        when :belongs_to
          if options[:polymorphic]
            Associations::BelongsToPolymorphicAssociation
          else
            Associations::BelongsToAssociation
          end
        when :has_and_belongs_to_many
          Associations::HasAndBelongsToManyAssociation
        when :has_many
          if options[:through]
            Associations::HasManyThroughAssociation
          else
            Associations::HasManyAssociation
          end
        when :has_one
          if options[:through]
            Associations::HasOneThroughAssociation
          else
            Associations::HasOneAssociation
          end
        end
      end

      private
        def derive_class_name
          class_name = name.to_s.camelize
          class_name = class_name.singularize if collection?
          class_name
        end

        def derive_foreign_key
          if belongs_to?
            "#{name}_id"
          elsif options[:as]
            "#{options[:as]}_id"
          else
            active_record.name.foreign_key
          end
        end

        def primary_key(klass)
          klass.primary_key || raise(UnknownPrimaryKey.new(klass))
        end
    end

    # Holds all the meta-data about a :through association as it was specified
    # in the Active Record class.
    class ThroughReflection < AssociationReflection #:nodoc:
      delegate :foreign_key, :foreign_type, :association_foreign_key,
               :active_record_primary_key, :type, :to => :source_reflection

      # Gets the source of the through reflection. It checks both a singularized
      # and pluralized form for <tt>:belongs_to</tt> or <tt>:has_many</tt>.
      #
      #   class Post < ActiveRecord::Base
      #     has_many :taggings
      #     has_many :tags, :through => :taggings
      #   end
      #
      def source_reflection
        @source_reflection ||= source_reflection_names.collect { |name| through_reflection.klass.reflect_on_association(name) }.compact.first
      end

      # Returns the AssociationReflection object specified in the <tt>:through</tt> option
      # of a HasManyThrough or HasOneThrough association.
      #
      #   class Post < ActiveRecord::Base
      #     has_many :taggings
      #     has_many :tags, :through => :taggings
      #   end
      #
      #   tags_reflection = Post.reflect_on_association(:tags)
      #   taggings_reflection = tags_reflection.through_reflection
      #
      def through_reflection
        @through_reflection ||= active_record.reflect_on_association(options[:through])
      end

      # Returns an array of reflections which are involved in this association. Each item in the
      # array corresponds to a table which will be part of the query for this association.
      #
      # The chain is built by recursively calling #chain on the source reflection and the through
      # reflection. The base case for the recursion is a normal association, which just returns
      # [self] as its #chain.
      def chain
        @chain ||= begin
          chain = source_reflection.chain + through_reflection.chain
          chain[0] = self # Use self so we don't lose the information from :source_type
          chain
        end
      end

      # Consider the following example:
      #
      #   class Person
      #     has_many :articles
      #     has_many :comment_tags, :through => :articles
      #   end
      #
      #   class Article
      #     has_many :comments
      #     has_many :comment_tags, :through => :comments, :source => :tags
      #   end
      #
      #   class Comment
      #     has_many :tags
      #   end
      #
      # There may be conditions on Person.comment_tags, Article.comment_tags and/or Comment.tags,
      # but only Comment.tags will be represented in the #chain. So this method creates an array
      # of conditions corresponding to the chain. Each item in the #conditions array corresponds
      # to an item in the #chain, and is itself an array of conditions from an arbitrary number
      # of relevant reflections, plus any :source_type or polymorphic :as constraints.
      def conditions
        @conditions ||= begin
          conditions = source_reflection.conditions.map { |c| c.dup }

          # Add to it the conditions from this reflection if necessary.
          conditions.first << options[:conditions] if options[:conditions]

          through_conditions = through_reflection.conditions

          if options[:source_type]
            through_conditions.first << { foreign_type => options[:source_type] }
          end

          # Recursively fill out the rest of the array from the through reflection
          conditions += through_conditions

          # And return
          conditions
        end
      end

      # The macro used by the source association
      def source_macro
        source_reflection.source_macro
      end

      # A through association is nested if there would be more than one join table
      def nested?
        chain.length > 2 || through_reflection.macro == :has_and_belongs_to_many
      end

      # We want to use the klass from this reflection, rather than just delegate straight to
      # the source_reflection, because the source_reflection may be polymorphic. We still
      # need to respect the source_reflection's :primary_key option, though.
      def association_primary_key(klass = nil)
        # Get the "actual" source reflection if the immediate source reflection has a
        # source reflection itself
        source_reflection = self.source_reflection
        while source_reflection.source_reflection
          source_reflection = source_reflection.source_reflection
        end

        source_reflection.options[:primary_key] || primary_key(klass || self.klass)
      end

      # Gets an array of possible <tt>:through</tt> source reflection names:
      #
      #   [:singularized, :pluralized]
      #
      def source_reflection_names
        @source_reflection_names ||= (options[:source] ? [options[:source]] : [name.to_s.singularize, name]).collect { |n| n.to_sym }
      end

      def source_options
        source_reflection.options
      end

      def through_options
        through_reflection.options
      end

      def check_validity!
        if through_reflection.nil?
          raise HasManyThroughAssociationNotFoundError.new(active_record.name, self)
        end

        if through_reflection.options[:polymorphic]
          raise HasManyThroughAssociationPolymorphicThroughError.new(active_record.name, self)
        end

        if source_reflection.nil?
          raise HasManyThroughSourceAssociationNotFoundError.new(self)
        end

        if options[:source_type] && source_reflection.options[:polymorphic].nil?
          raise HasManyThroughAssociationPointlessSourceTypeError.new(active_record.name, self, source_reflection)
        end

        if source_reflection.options[:polymorphic] && options[:source_type].nil?
          raise HasManyThroughAssociationPolymorphicSourceError.new(active_record.name, self, source_reflection)
        end

        if macro == :has_one && through_reflection.collection?
          raise HasOneThroughCantAssociateThroughCollection.new(active_record.name, self, through_reflection)
        end

        check_validity_of_inverse!
      end

      private
        def derive_class_name
          # get the class_name of the belongs_to association of the through reflection
          options[:source_type] || source_reflection.class_name
        end
    end
  end
end