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Enable has_many :through for going through a has_one association on t…

…he join model [#2719 state:resolved]

Signed-off-by: Pratik Naik <pratiknaik@gmail.com>
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commit 00d6c766608f90ce64f11feb98786cbc7f71b89d 1 parent 810b59a
@gtd gtd authored lifo committed
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31 activerecord/lib/active_record/associations.rb
@@ -42,11 +42,12 @@ def initialize(reflection)
end
end
- class HasManyThroughCantAssociateThroughHasManyReflection < ActiveRecordError #:nodoc:
+ class HasManyThroughCantAssociateThroughHasOneOrManyReflection < ActiveRecordError #:nodoc:
def initialize(owner, reflection)
super("Cannot modify association '#{owner.class.name}##{reflection.name}' because the source reflection class '#{reflection.source_reflection.class_name}' is associated to '#{reflection.through_reflection.class_name}' via :#{reflection.source_reflection.macro}.")
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.")
@@ -416,6 +417,32 @@ def association_instance_set(name, association)
# @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.
#
+ # Similarly you can go through a +has_one+ association on the join model:
+ #
+ # class Group < ActiveRecord::Base
+ # has_many :users
+ # has_many :avatars, :through => :users
+ # end
+ #
+ # class User < ActiveRecord::Base
+ # belongs_to :group
+ # has_one :avatar
+ # end
+ #
+ # class Avatar < ActiveRecord::Base
+ # belongs_to :user
+ # end
+ #
+ # @group = Group.first
+ # @group.users.collect { |u| u.avatar }.flatten # select all avatars for all users in the group
+ # @group.avatars # selects all avatars by going through the User join model.
+ #
+ # An important caveat with going through +has_one+ or +has_many+ associations on the join model is that these associations are
+ # *read-only*. For example, the following would not work following the previous example:
+ #
+ # @group.avatars << Avatar.new # this would work if User belonged_to Avatar rather than the other way around.
+ # @group.avatars.delete(@group.avatars.last) # so would this
+ #
# === Polymorphic Associations
#
# Polymorphic associations on models are not restricted on what types of models they can be associated with. Rather, they
@@ -819,7 +846,7 @@ module ClassMethods
# [:through]
# Specifies a Join Model through which to perform the query. 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 on the join model.
+ # <tt>has_one</tt> or <tt>has_many</tt> association on the join model.
# [:source]
# 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 <tt>:subscribers</tt> or
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2  activerecord/lib/active_record/associations/through_association_scope.rb
@@ -93,7 +93,7 @@ def construct_owner_attributes(reflection)
# Construct attributes for :through pointing to owner and associate.
def construct_join_attributes(associate)
# TODO: revist this to allow it for deletion, supposing dependent option is supported
- raise ActiveRecord::HasManyThroughCantAssociateThroughHasManyReflection.new(@owner, @reflection) if @reflection.source_reflection.macro == :has_many
+ raise ActiveRecord::HasManyThroughCantAssociateThroughHasOneOrManyReflection.new(@owner, @reflection) if [:has_one, :has_many].include?(@reflection.source_reflection.macro)
join_attributes = construct_owner_attributes(@reflection.through_reflection).merge(@reflection.source_reflection.primary_key_name => associate.id)
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2  activerecord/lib/active_record/reflection.rb
@@ -314,7 +314,7 @@ def check_validity!
raise HasManyThroughAssociationPolymorphicError.new(active_record.name, self, source_reflection)
end
- unless [:belongs_to, :has_many].include?(source_reflection.macro) && source_reflection.options[:through].nil?
+ unless [:belongs_to, :has_many, :has_one].include?(source_reflection.macro) && source_reflection.options[:through].nil?
raise HasManyThroughSourceAssociationMacroError.new(self)
end
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2  activerecord/test/cases/associations/has_many_associations_test.rb
@@ -898,7 +898,7 @@ def test_modifying_a_through_a_has_many_should_raise
lambda { authors(:mary).comments = [comments(:greetings), comments(:more_greetings)] },
lambda { authors(:mary).comments << Comment.create!(:body => "Yay", :post_id => 424242) },
lambda { authors(:mary).comments.delete(authors(:mary).comments.first) },
- ].each {|block| assert_raise(ActiveRecord::HasManyThroughCantAssociateThroughHasManyReflection, &block) }
+ ].each {|block| assert_raise(ActiveRecord::HasManyThroughCantAssociateThroughHasOneOrManyReflection, &block) }
end
def test_dynamic_find_should_respect_association_order_for_through
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12 activerecord/test/cases/associations/has_many_through_associations_test.rb
@@ -304,4 +304,16 @@ def test_find_on_has_many_association_collection_with_include_and_conditions
post_with_no_comments = people(:michael).posts_with_no_comments.first
assert_equal post_with_no_comments, posts(:authorless)
end
+
+ def test_has_many_through_has_one_reflection
+ assert_equal [comments(:eager_sti_on_associations_vs_comment)], authors(:david).very_special_comments
+ end
+
+ def test_modifying_has_many_through_has_one_reflection_should_raise
+ [
+ lambda { authors(:david).very_special_comments = [VerySpecialComment.create!(:body => "Gorp!", :post_id => 1011), VerySpecialComment.create!(:body => "Eep!", :post_id => 1012)] },
+ lambda { authors(:david).very_special_comments << VerySpecialComment.create!(:body => "Hoohah!", :post_id => 1013) },
+ lambda { authors(:david).very_special_comments.delete(authors(:david).very_special_comments.first) },
+ ].each {|block| assert_raise(ActiveRecord::HasManyThroughCantAssociateThroughHasOneOrManyReflection, &block) }
+ end
end
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2  activerecord/test/cases/associations/join_model_test.rb
@@ -381,7 +381,7 @@ def test_has_many_through_has_many_find_by_id
end
def test_has_many_through_polymorphic_has_one
- assert_raise(ActiveRecord::HasManyThroughSourceAssociationMacroError) { authors(:david).tagging }
+ assert_equal Tagging.find(1,2), authors(:david).tagging
end
def test_has_many_through_polymorphic_has_many
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1  activerecord/test/models/author.rb
@@ -1,5 +1,6 @@
class Author < ActiveRecord::Base
has_many :posts
+ has_many :very_special_comments, :through => :posts
has_many :posts_with_comments, :include => :comments, :class_name => "Post"
has_many :popular_grouped_posts, :include => :comments, :class_name => "Post", :group => "type", :having => "SUM(comments_count) > 1", :select => "type"
has_many :posts_with_comments_sorted_by_comment_id, :include => :comments, :class_name => "Post", :order => 'comments.id'
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