aboutsummaryrefslogtreecommitdiffstats
path: root/activerecord/lib/active_record/associations/association.rb
blob: 1cb2b2d7c688f1fc2842d91b4123efed2bb74a36 (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
require "active_support/core_ext/array/wrap"

module ActiveRecord
  module Associations
    # = Active Record Associations
    #
    # This is the root class of all associations ('+ Foo' signifies an included module Foo):
    #
    #   Association
    #     SingularAssociation
    #       HasOneAssociation + ForeignAssociation
    #         HasOneThroughAssociation + ThroughAssociation
    #       BelongsToAssociation
    #         BelongsToPolymorphicAssociation
    #     CollectionAssociation
    #       HasManyAssociation + ForeignAssociation
    #         HasManyThroughAssociation + ThroughAssociation
    class Association #:nodoc:
      attr_reader :owner, :target, :reflection
      attr_accessor :inversed

      delegate :options, to: :reflection

      def initialize(owner, reflection)
        reflection.check_validity!

        @owner, @reflection = owner, reflection

        reset
        reset_scope
      end

      # Returns the name of the table of the associated class:
      #
      #   post.comments.aliased_table_name # => "comments"
      #
      def aliased_table_name
        klass.table_name
      end

      # Resets the \loaded flag to +false+ and sets the \target to +nil+.
      def reset
        @loaded = false
        @target = nil
        @stale_state = nil
        @inversed = false
      end

      # Reloads the \target and returns +self+ on success.
      def reload
        reset
        reset_scope
        load_target
        self unless target.nil?
      end

      # Has the \target been already \loaded?
      def loaded?
        @loaded
      end

      # Asserts the \target has been loaded setting the \loaded flag to +true+.
      def loaded!
        @loaded = true
        @stale_state = stale_state
        @inversed = false
      end

      # The target is stale if the target no longer points to the record(s) that the
      # relevant foreign_key(s) refers to. If stale, the association accessor method
      # on the owner will reload the target. It's up to subclasses to implement the
      # stale_state method if relevant.
      #
      # Note that if the target has not been loaded, it is not considered stale.
      def stale_target?
        !inversed && loaded? && @stale_state != stale_state
      end

      # Sets the target of this association to <tt>\target</tt>, and the \loaded flag to +true+.
      def target=(target)
        @target = target
        loaded!
      end

      def scope
        target_scope.merge!(association_scope)
      end

      # The scope for this association.
      #
      # Note that the association_scope is merged into the target_scope only when the
      # scope method is called. This is because at that point the call may be surrounded
      # by scope.scoping { ... } or with_scope { ... } etc, which affects the scope which
      # actually gets built.
      def association_scope
        if klass
          @association_scope ||= AssociationScope.scope(self, klass.connection)
        end
      end

      def reset_scope
        @association_scope = nil
      end

      # Set the inverse association, if possible
      def set_inverse_instance(record)
        if invertible_for?(record)
          inverse = record.association(inverse_reflection_for(record).name)
          inverse.target = owner
          inverse.inversed = true
        end
        record
      end

      # Remove the inverse association, if possible
      def remove_inverse_instance(record)
        if invertible_for?(record)
          inverse = record.association(inverse_reflection_for(record).name)
          inverse.target = nil
          inverse.inversed = false
        end
      end

      # Returns the class of the target. belongs_to polymorphic overrides this to look at the
      # polymorphic_type field on the owner.
      def klass
        reflection.klass
      end

      # Can be overridden (i.e. in ThroughAssociation) to merge in other scopes (i.e. the
      # through association's scope)
      def target_scope
        AssociationRelation.create(klass, klass.arel_table, klass.predicate_builder, self).merge!(klass.all)
      end

      # Loads the \target if needed and returns it.
      #
      # This method is abstract in the sense that it relies on +find_target+,
      # which is expected to be provided by descendants.
      #
      # If the \target is already \loaded it is just returned. Thus, you can call
      # +load_target+ unconditionally to get the \target.
      #
      # ActiveRecord::RecordNotFound is rescued within the method, and it is
      # not reraised. The proxy is \reset and +nil+ is the return value.
      def load_target
        @target = find_target if (@stale_state && stale_target?) || find_target?

        loaded! unless loaded?
        target
      rescue ActiveRecord::RecordNotFound
        reset
      end

      def interpolate(sql, record = nil)
        if sql.respond_to?(:to_proc)
          owner.instance_exec(record, &sql)
        else
          sql
        end
      end

      # We can't dump @reflection since it contains the scope proc
      def marshal_dump
        ivars = (instance_variables - [:@reflection]).map { |name| [name, instance_variable_get(name)] }
        [@reflection.name, ivars]
      end

      def marshal_load(data)
        reflection_name, ivars = data
        ivars.each { |name, val| instance_variable_set(name, val) }
        @reflection = @owner.class._reflect_on_association(reflection_name)
      end

      def initialize_attributes(record, except_from_scope_attributes = nil) #:nodoc:
        except_from_scope_attributes ||= {}
        skip_assign = [reflection.foreign_key, reflection.type].compact
        assigned_keys = record.changed_attribute_names_to_save
        assigned_keys += except_from_scope_attributes.keys.map(&:to_s)
        attributes = create_scope.except(*(assigned_keys - skip_assign))
        record.assign_attributes(attributes)
        set_inverse_instance(record)
      end

      def create(attributes = {}, &block)
        _create_record(attributes, &block)
      end

      def create!(attributes = {}, &block)
        _create_record(attributes, true, &block)
      end

      private

        def find_target?
          !loaded? && (!owner.new_record? || foreign_key_present?) && klass
        end

        def creation_attributes
          attributes = {}

          if (reflection.has_one? || reflection.collection?) && !options[:through]
            attributes[reflection.foreign_key] = owner[reflection.active_record_primary_key]

            if reflection.options[:as]
              attributes[reflection.type] = owner.class.base_class.name
            end
          end

          attributes
        end

        # Sets the owner attributes on the given record
        def set_owner_attributes(record)
          creation_attributes.each { |key, value| record[key] = value }
        end

        # Returns true if there is a foreign key present on the owner which
        # references the target. This is used to determine whether we can load
        # the target if the owner is currently a new record (and therefore
        # without a key). If the owner is a new record then foreign_key must
        # be present in order to load target.
        #
        # Currently implemented by belongs_to (vanilla and polymorphic) and
        # has_one/has_many :through associations which go through a belongs_to.
        def foreign_key_present?
          false
        end

        # Raises ActiveRecord::AssociationTypeMismatch unless +record+ is of
        # the kind of the class of the associated objects. Meant to be used as
        # a sanity check when you are about to assign an associated record.
        def raise_on_type_mismatch!(record)
          unless record.is_a?(reflection.klass)
            fresh_class = reflection.class_name.safe_constantize
            unless fresh_class && record.is_a?(fresh_class)
              message = "#{reflection.class_name}(##{reflection.klass.object_id}) expected, "\
                "got #{record.inspect} which is an instance of #{record.class}(##{record.class.object_id})"
              raise ActiveRecord::AssociationTypeMismatch, message
            end
          end
        end

        # Can be redefined by subclasses, notably polymorphic belongs_to
        # The record parameter is necessary to support polymorphic inverses as we must check for
        # the association in the specific class of the record.
        def inverse_reflection_for(record)
          reflection.inverse_of
        end

        # Returns true if inverse association on the given record needs to be set.
        # This method is redefined by subclasses.
        def invertible_for?(record)
          foreign_key_for?(record) && inverse_reflection_for(record)
        end

        # Returns true if record contains the foreign_key
        def foreign_key_for?(record)
          record.has_attribute?(reflection.foreign_key)
        end

        # This should be implemented to return the values of the relevant key(s) on the owner,
        # so that when stale_state is different from the value stored on the last find_target,
        # the target is stale.
        #
        # This is only relevant to certain associations, which is why it returns +nil+ by default.
        def stale_state
        end

        def build_record(attributes)
          reflection.build_association(attributes) do |record|
            initialize_attributes(record, attributes)
          end
        end

        # Returns true if statement cache should be skipped on the association reader.
        def skip_statement_cache?
          reflection.has_scope? ||
            scope.eager_loading? ||
            klass.scope_attributes? ||
            reflection.source_reflection.active_record.default_scopes.any?
        end
    end
  end
end