Extract `associate_records_to_owner` to refactor `Preloader::Association`

Since we have `Preloader#preload`, `Preloader::Association#preload` is a
little confusing. And also, since the `preload` method is an abstract
method, it is hard to read where `associated_records_by_owner` is
called. This refactors `Preloader::Association` to ease to read where
`associated_records_by_owner` is called.

3 files changed, 14 insertions, 20 deletions

diff --git a/activerecord/lib/active_record/associations/preloader/association.rb b/activerecord/lib/active_record/associations/preloader/association.rb
index 9bb6a613e1..323f25e37e 100644
--- a/activerecord/lib/active_record/associations/preloader/association.rb
+++ b/activerecord/lib/active_record/associations/preloader/association.rb
@@ -17,11 +17,9 @@ module ActiveRecord
         end
 
         def run(preloader)
-          preload(preloader)
-        end
-
-        def preload(preloader)
-          raise NotImplementedError
+          associated_records_by_owner(preloader).each do |owner, records|
+            associate_records_to_owner(owner, records)
+          end
         end
 
         # The name of the key on the associated records
@@ -51,6 +49,10 @@ module ActiveRecord
             end
           end
 
+          def associate_records_to_owner(owner, records)
+            raise NotImplementedError
+          end
+
           def owner_keys
             unless defined?(@owner_keys)
               @owner_keys = owners.map do |owner|
diff --git a/activerecord/lib/active_record/associations/preloader/collection_association.rb b/activerecord/lib/active_record/associations/preloader/collection_association.rb
index fb920a642c..fc2029f54a 100644
--- a/activerecord/lib/active_record/associations/preloader/collection_association.rb
+++ b/activerecord/lib/active_record/associations/preloader/collection_association.rb
@@ -5,13 +5,10 @@ module ActiveRecord
     class Preloader
       class CollectionAssociation < Association #:nodoc:
         private
-
-          def preload(preloader)
-            associated_records_by_owner(preloader).each do |owner, records|
-              association = owner.association(reflection.name)
-              association.loaded!
-              association.target.concat(records)
-            end
+          def associate_records_to_owner(owner, records)
+            association = owner.association(reflection.name)
+            association.loaded!
+            association.target.concat(records)
           end
       end
     end
diff --git a/activerecord/lib/active_record/associations/preloader/singular_association.rb b/activerecord/lib/active_record/associations/preloader/singular_association.rb
index 266b5f6b1c..30a92411e3 100644
--- a/activerecord/lib/active_record/associations/preloader/singular_association.rb
+++ b/activerecord/lib/active_record/associations/preloader/singular_association.rb
@@ -5,14 +5,9 @@ module ActiveRecord
     class Preloader
       class SingularAssociation < Association #:nodoc:
         private
-
-          def preload(preloader)
-            associated_records_by_owner(preloader).each do |owner, associated_records|
-              record = associated_records.first
-
-              association = owner.association(reflection.name)
-              association.target = record
-            end
+          def associate_records_to_owner(owner, records)
+            association = owner.association(reflection.name)
+            association.target = records.first
           end
       end
     end