transforms type for polymorphic relationships too

lib/fast_jsonapi/object_serializer.rb

@@ -249,7 +249,8 @@ module FastJsonapi
           relationship_type: relationship_type,
           cached: options[:cached],
           polymorphic: fetch_polymorphic_option(options),
-          conditional_proc: options[:if]
+          conditional_proc: options[:if],
+          transform_method: @transform_method
         )
       end
 

lib/fast_jsonapi/relationship.rb

@@ -1,6 +1,6 @@
 module FastJsonapi
   class Relationship
-    attr_reader :key, :name, :id_method_name, :record_type, :object_method_name, :object_block, :serializer, :relationship_type, :cached, :polymorphic, :conditional_proc
+    attr_reader :key, :name, :id_method_name, :record_type, :object_method_name, :object_block, :serializer, :relationship_type, :cached, :polymorphic, :conditional_proc, :transform_method
 
     def initialize(
       key:,
@@ -13,7 +13,8 @@ module FastJsonapi
       relationship_type:,
       cached: false,
       polymorphic:,
-      conditional_proc:
+      conditional_proc:,
+      transform_method:
     )
       @key = key
       @name = name
@@ -26,6 +27,7 @@ module FastJsonapi
       @cached = cached
       @polymorphic = polymorphic
       @conditional_proc = conditional_proc
+      @transform_method = transform_method
     end
 
     def serialize(record, serialization_params, output_hash)
@@ -68,7 +70,7 @@ module FastJsonapi
 
     def id_hash_from_record(record, record_types)
       # memoize the record type within the record_types dictionary, then assigning to record_type:
-      associated_record_type = record_types[record.class] ||= record.class.name.demodulize.underscore.to_sym
+      associated_record_type = record_types[record.class] ||= run_key_transform(record.class.name.demodulize.underscore)
       id_hash(record.id, associated_record_type)
     end
 
@@ -93,5 +95,13 @@ module FastJsonapi
       end
       record.public_send(id_method_name)
     end
+
+    def run_key_transform(input)
+      if self.transform_method.present?
+        input.to_s.send(*self.transform_method).to_sym
+      else
+        input.to_sym
+      end
+    end
   end
 end

spec/lib/object_serializer_polymorphic_spec.rb

@@ -0,0 +1,51 @@
+require 'spec_helper'
+
+describe FastJsonapi::ObjectSerializer do
+  class List
+    attr_accessor :id, :name, :items
+  end
+
+  class ChecklistItem
+    attr_accessor :id, :name
+  end
+
+  class Car
+    attr_accessor :id, :model, :year
+  end
+
+  class ListSerializer
+    include FastJsonapi::ObjectSerializer
+    set_type :list
+    attributes :name
+    set_key_transform :dash
+    has_many :items, polymorphic: true
+  end
+
+  let(:car) do
+    car = Car.new
+    car.id = 1
+    car.model = 'Toyota Corolla'
+    car.year = 1987
+    car
+  end
+
+  let(:checklist_item) do
+    checklist_item = ChecklistItem.new
+    checklist_item.id = 2
+    checklist_item.name = 'Do this action!'
+    checklist_item
+  end
+
+  context 'when serializing id and type of polymorphic relationships' do
+    it 'should return correct type when transform_method is specified' do
+      list = List.new
+      list.id = 1
+      list.items = [checklist_item, car]
+      list_hash = ListSerializer.new(list).to_hash
+      record_type = list_hash[:data][:relationships][:items][:data][0][:type]
+      expect(record_type).to eq 'checklist-item'.to_sym
+      record_type = list_hash[:data][:relationships][:items][:data][1][:type]
+      expect(record_type).to eq 'car'.to_sym
+    end
+  end
+end