Add option to specify custom method for has_many relationships creation

lib/jsonapi/basic_resource.rb

@@ -246,10 +246,9 @@ def reflect_relationship?(relationship, options)
 
     def _create_to_many_links(relationship_type, relationship_key_values, options)
       relationship = self.class._relationships[relationship_type]
-      relation_name = relationship.relation_name(context: @context)
 
       if options[:reflected_source]
-        @model.public_send(relation_name) << options[:reflected_source]._model
+        _create_to_many_link(relationship, options[:reflected_source])
         return :completed
       end
 
@@ -274,15 +273,24 @@ def _create_to_many_links(relationship_type, relationship_key_values, options)
           end
           @reload_needed = true
         else
-          unless @model.public_send(relation_name).include?(related_resource._model)
-            @model.public_send(relation_name) << related_resource._model
-          end
+          _create_to_many_link(relationship, related_resource)
         end
       end
 
       :completed
     end
 
+    def _create_to_many_link(relationship, related_resource)
+      relation_name = relationship.relation_name(context: @context)
+      return if @model.public_send(relation_name).include?(related_resource._model)
+
+      if relationship.options[:create_method]
+        public_send(relationship.options.fetch(:create_method), related_resource._model)
+      else
+        @model.public_send(relation_name) << related_resource._model
+      end
+    end
+
     def _replace_to_many_links(relationship_type, relationship_key_values, options)
       relationship = self.class._relationship(relationship_type)
 

test/controllers/controller_test.rb

@@ -1637,6 +1637,40 @@ def test_create_relationship_to_many_join_table_record_exists
     assert_equal [502,503,505], post_object.tag_ids
   end
 
+  def test_create_relationship_to_many_with_create_method_option
+    PostResource.class_eval do
+      has_many :super_tags, acts_as_set: true, relation_name: :special_tags, class_name: 'Tag',
+                            create_method: :add_super_tag
+      def add_super_tag(tag)
+        tag.update!(name: "#{tag.name}[super]")
+        @model.special_post_tags.create!(tag: tag)
+      end
+    end
+
+    set_content_type_header!
+
+    tag_502_name = Tag.find(502).name
+    tag_503_name = Tag.find(503).name
+
+    put :create_relationship, params: {post_id: 3, relationship: 'super_tags', data: [{type: 'tags', id: 502}, {type: 'tags', id: 503}]}
+
+    assert_response :no_content
+    post_object = Post.find(3)
+    assert_equal 2, post_object.special_tags.collect { |tag| tag.id }.length
+    assert matches_array? [502, 503], post_object.special_tags.collect { |tag| tag.id }
+    assert_equal "#{tag_502_name}[super]", Tag.find(502).name
+    assert_equal "#{tag_503_name}[super]", Tag.find(503).name
+
+    tag_505_name = Tag.find(505).name
+
+    post :create_relationship, params: {post_id: 3, relationship: 'super_tags', data: [{type: 'tags', id: 502}, {type: 'tags', id: 505}]}
+
+    assert_response :no_content
+    post_object.reload
+    assert_equal [502,503,505], post_object.special_tag_ids
+    assert_equal "#{tag_505_name}[super]", Tag.find(505).name
+  end
+
   def test_update_relationship_to_many_missing_tags
     set_content_type_header!
     put :update_relationship, params: {post_id: 3, relationship: 'tags'}

test/test_helper.rb

@@ -62,7 +62,9 @@ class TestApp < Rails::Application
   config.active_support.halt_callback_chains_on_return_false = false
   config.active_record.time_zone_aware_types = [:time, :datetime]
   config.active_record.belongs_to_required_by_default = false
-  unless Rails::VERSION::MAJOR == 5 && Rails::VERSION::MINOR < 2 || Rails::VERSION::MAJOR == 6 && Rails::VERSION::MINOR >= 1
+  unless Rails::VERSION::MAJOR == 5 && Rails::VERSION::MINOR < 2 ||
+           Rails::VERSION::MAJOR == 6 && Rails::VERSION::MINOR >= 1 ||
+           Rails::VERSION::MAJOR > 6
     config.active_record.sqlite3.represent_boolean_as_integer = true
   end
 end
@@ -221,6 +223,7 @@ class CatResource < JSONAPI::Resource
   jsonapi_resources :posts do
     jsonapi_relationships
     jsonapi_links :special_tags
+    jsonapi_links :super_tags, only: [:create]
   end
   jsonapi_resources :sections
   jsonapi_resources :iso_currencies