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
|
require 'active_support/core_ext/array/wrap'
module ActiveRecord
module Associations
# = Active Record Associations
#
# This is the root class of all association proxies ('+ Foo' signifies an included module Foo):
#
# AssociationProxy
# BelongsToAssociation
# BelongsToPolymorphicAssociation
# AssociationCollection
# HasAndBelongsToManyAssociation
# HasManyAssociation
# HasManyThroughAssociation + ThroughAssociation
# HasOneAssociation
# HasOneThroughAssociation + ThroughAssociation
#
# Association proxies in Active Record are middlemen between the object that
# holds the association, known as the <tt>@owner</tt>, and the actual associated
# object, known as the <tt>@target</tt>. The kind of association any proxy is
# about is available in <tt>@reflection</tt>. That's an instance of the class
# ActiveRecord::Reflection::AssociationReflection.
#
# For example, given
#
# class Blog < ActiveRecord::Base
# has_many :posts
# end
#
# blog = Blog.find(:first)
#
# the association proxy in <tt>blog.posts</tt> has the object in +blog+ as
# <tt>@owner</tt>, the collection of its posts as <tt>@target</tt>, and
# the <tt>@reflection</tt> object represents a <tt>:has_many</tt> macro.
#
# This class has most of the basic instance methods removed, and delegates
# unknown methods to <tt>@target</tt> via <tt>method_missing</tt>. As a
# corner case, it even removes the +class+ method and that's why you get
#
# blog.posts.class # => Array
#
# though the object behind <tt>blog.posts</tt> is not an Array, but an
# ActiveRecord::Associations::HasManyAssociation.
#
# The <tt>@target</tt> object is not \loaded until needed. For example,
#
# blog.posts.count
#
# is computed directly through SQL and does not trigger by itself the
# instantiation of the actual post records.
class AssociationProxy #:nodoc:
alias_method :proxy_extend, :extend
delegate :to_param, :to => :proxy_target
instance_methods.each { |m| undef_method m unless m.to_s =~ /^(?:nil\?|send|object_id|to_a)$|^__|^respond_to|proxy_/ }
def initialize(owner, reflection)
@owner, @reflection = owner, reflection
@updated = false
reflection.check_validity!
Array.wrap(reflection.options[:extend]).each { |ext| proxy_extend(ext) }
reset
construct_scope
end
# Returns the owner of the proxy.
def proxy_owner
@owner
end
# Returns the reflection object that represents the association handled
# by the proxy.
def proxy_reflection
@reflection
end
# Does the proxy or its \target respond to +symbol+?
def respond_to?(*args)
super || (load_target && @target.respond_to?(*args))
end
# Forwards <tt>===</tt> explicitly to the \target because the instance method
# removal above doesn't catch it. Loads the \target if needed.
def ===(other)
load_target
other === @target
end
# Returns the name of the table of the related class:
#
# post.comments.aliased_table_name # => "comments"
#
def aliased_table_name
@reflection.klass.table_name
end
# Returns the SQL string that corresponds to the <tt>:conditions</tt>
# option of the macro, if given, or +nil+ otherwise.
def conditions
@conditions ||= interpolate_sql(@reflection.sanitized_conditions) if @reflection.sanitized_conditions
end
alias :sql_conditions :conditions
# Resets the \loaded flag to +false+ and sets the \target to +nil+.
def reset
@loaded = false
@target = nil
end
# Reloads the \target and returns +self+ on success.
def reload
reset
construct_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
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
# state_state method if relevant.
#
# Note that if the target has not been loaded, it is not considered stale.
def stale_target?
loaded? && @stale_state != stale_state
end
# Returns the target of this proxy, same as +proxy_target+.
attr_reader :target
# Returns the \target of the proxy, same as +target+.
alias :proxy_target :target
# Sets the target of this proxy to <tt>\target</tt>, and the \loaded flag to +true+.
def target=(target)
@target = target
loaded
end
# Forwards the call to the target. Loads the \target if needed.
def inspect
load_target
@target.inspect
end
def send(method, *args)
if respond_to?(method)
super
else
load_target
@target.send(method, *args)
end
end
def scoped
target_scope & @association_scope
end
protected
def interpolate_sql(sql, record = nil)
@owner.send(:interpolate_sql, sql, record)
end
# Forwards the call to the reflection class.
def sanitize_sql(sql, table_name = @reflection.klass.table_name)
@reflection.klass.send(:sanitize_sql, sql, table_name)
end
# Construct the scope for this association.
#
# Note that the association_scope is merged into the targed_scope only when the
# scoped 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 construct_scope
@association_scope = association_scope if target_klass
end
def association_scope
scope = target_klass.unscoped
scope = scope.create_with(creation_attributes)
scope = scope.apply_finder_options(@reflection.options.slice(:conditions, :readonly, :include))
scope = scope.where(construct_owner_conditions)
scope = scope.select(select_value) if select_value = self.select_value
scope
end
def select_value
@reflection.options[:select]
end
# Implemented by (some) subclasses
def creation_attributes
{ }
end
def aliased_table
target_klass.arel_table
end
# Set the inverse association, if possible
def set_inverse_instance(record)
if record && invertible_for?(record)
inverse = record.send(:association_proxy, inverse_reflection_for(record).name)
inverse.target = @owner
end
end
# This class of the target. belongs_to polymorphic overrides this to look at the
# polymorphic_type field on the owner.
def target_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
target_klass.scoped
end
# Returns a hash linking the owner to the association represented by the reflection
def construct_owner_attributes(reflection = @reflection)
attributes = {}
if reflection.macro == :belongs_to
attributes[reflection.association_primary_key] = @owner[reflection.foreign_key]
else
attributes[reflection.foreign_key] = @owner[reflection.active_record_primary_key]
if reflection.options[:as]
attributes["#{reflection.options[:as]}_type"] = @owner.class.base_class.name
end
end
attributes
end
# Builds an array of arel nodes from the owner attributes hash
def construct_owner_conditions(table = aliased_table, reflection = @reflection)
conditions = construct_owner_attributes(reflection).map do |attr, value|
table[attr].eq(value)
end
table.create_and(conditions)
end
# Sets the owner attributes on the given record
def set_owner_attributes(record)
if @owner.persisted?
construct_owner_attributes.each { |key, value| record[key] = value }
end
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
if !loaded? && (!@owner.new_record? || foreign_key_present?) && target_klass
@target = find_target
end
loaded
@target
rescue ActiveRecord::RecordNotFound
reset
end
private
# Forwards any missing method call to the \target.
def method_missing(method, *args, &block)
if load_target
return super unless @target.respond_to?(method)
@target.send(method, *args, &block)
end
rescue NoMethodError => e
raise e, e.message.sub(/ for #<.*$/, " via proxy for #{@target}")
end
# Should be 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).
#
# 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) || record.is_a?(@reflection.class_name.constantize)
message = "#{@reflection.class_name}(##{@reflection.klass.object_id}) expected, got #{record.class}(##{record.class.object_id})"
raise ActiveRecord::AssociationTypeMismatch, message
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
# Is this association invertible? Can be redefined by subclasses.
def invertible_for?(record)
inverse_reflection_for(record)
end
# This should be implemented to return the values of the relevant key(s) on the owner,
# so that when state_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
nil
end
end
end
end
|