Specify insert_record with NotImplementedError in AssociationCollection, to indicate that subclasses should implement it. Also add save_record to reduce duplication.

activerecord/lib/active_record/associations/association_collection.rb

@@ -476,6 +476,17 @@ module ActiveRecord
         end
 
       private
+        # Do the relevant stuff to insert the given record into the association collection. The
+        # force param specifies whether or not an exception should be raised on failure. The
+        # validate param specifies whether validation should be performed (if force is false).
+        def insert_record(record, force = true, validate = true)
+          raise NotImplementedError
+        end
+
+        def save_record(record, force, validate)
+          force ? record.save! : record.save(:validate => validate)
+        end
+
         def create_record(attrs)
           attrs.update(@reflection.options[:conditions]) if @reflection.options[:conditions].is_a?(Hash)
           ensure_owner_is_persisted!

activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb

@@ -35,11 +35,7 @@ module ActiveRecord
 
         def insert_record(record, force = true, validate = true)
           if record.new_record?
-            if force
-              record.save!
-            else
-              return false unless record.save(:validate => validate)
-            end
+            return false unless save_record(record, force, validate)
           end
 
           if @reflection.options[:insert_sql]

activerecord/lib/active_record/associations/has_many_association.rb

@@ -55,7 +55,7 @@ module ActiveRecord
 
         def insert_record(record, force = false, validate = true)
           set_belongs_to_association_for(record)
-          force ? record.save! : record.save(:validate => validate)
+          save_record(record, force, validate)
         end
 
         # Deletes the records according to the <tt>:dependent</tt> option.

activerecord/lib/active_record/associations/has_many_through_association.rb

@@ -60,11 +60,7 @@ module ActiveRecord
 
         def insert_record(record, force = true, validate = true)
           if record.new_record?
-            if force
-              record.save!
-            else
-              return false unless record.save(:validate => validate)
-            end
+            return false unless save_record(record, force, validate)
           end
 
           through_association = @owner.send(@reflection.through_reflection.name)