Add support to polymorphic models

Author: polmiro

lib/active_model/array_serializer.rb

@@ -15,6 +15,7 @@ def initialize(object, options={})
       @object          = object
       @scope           = options[:scope]
       @root            = options.fetch(:root, self.class._root)
+      @polymorphic   = options.fetch(:polymorphic, false)
       @meta_key        = options[:meta_key] || :meta
       @meta            = options[@meta_key]
       @each_serializer = options[:each_serializer]
@@ -33,7 +34,7 @@ def json_key
 
     def serializer_for(item)
       serializer_class = @each_serializer || Serializer.serializer_for(item) || DefaultSerializer
-      serializer_class.new(item, scope: scope, key_format: key_format, only: @only, except: @except)
+      serializer_class.new(item, scope: scope, key_format: key_format, only: @only, except: @except, polymorphic: @polymorphic)
     end
 
     def serializable_object

lib/active_model/serializer.rb

@@ -130,6 +130,7 @@ def initialize(object, options={})
       @object        = object
       @scope         = options[:scope]
       @root          = options.fetch(:root, self.class._root)
+      @polymorphic   = options.fetch(:polymorphic, false)
       @meta_key      = options[:meta_key] || :meta
       @meta          = options[@meta_key]
       @wrap_in_array = options[:_wrap_in_array]
@@ -138,7 +139,7 @@ def initialize(object, options={})
       @key_format    = options[:key_format]
       @context       = options[:context]
     end
-    attr_accessor :object, :scope, :root, :meta_key, :meta, :key_format, :context
+    attr_accessor :object, :scope, :root, :meta_key, :meta, :key_format, :context, :polymorphic
 
     def json_key
       key = if root == true || root.nil?
@@ -225,9 +226,9 @@ def serialize(association)
     def serialize_ids(association)
       associated_data = send(association.name)
       if associated_data.respond_to?(:to_ary)
-        associated_data.map { |elem| elem.read_attribute_for_serialization(association.embed_key) }
+        associated_data.map { |elem| serialize_id(elem, association) }
       else
-        associated_data.read_attribute_for_serialization(association.embed_key) if associated_data
+        serialize_id(associated_data, association) if associated_data
       end
     end
 
@@ -260,9 +261,19 @@ def serializable_object(options={})
       hash = attributes
       hash.merge! associations
       hash = convert_keys(hash) if key_format.present?
+      hash = { :type => type_name(@object), type_name(@object) => hash } if @polymorphic
       @wrap_in_array ? [hash] : hash
     end
     alias_method :serializable_hash, :serializable_object
+
+    def serialize_id(elem, association)
+      id = elem.read_attribute_for_serialization(association.embed_key)
+      association.polymorphic? ? { id: id, type: type_name(elem) } : id
+    end
+
+    def type_name(elem)
+      elem.class.to_s.demodulize.underscore.to_sym
+    end
   end
 
 end

lib/active_model/serializer/association.rb

@@ -15,6 +15,7 @@ def initialize(name, options={})
         @name          = name.to_s
         @options       = options
         self.embed     = options.fetch(:embed) { CONFIG.embed }
+        @polymorphic   = options.fetch(:polymorphic, false)
         @embed_in_root = options.fetch(:embed_in_root) { options.fetch(:include) { CONFIG.embed_in_root } }
         @key_format    = options.fetch(:key_format) { CONFIG.key_format }
         @embed_key     = options[:embed_key] || :id
@@ -27,13 +28,14 @@ def initialize(name, options={})
         @serializer_from_options = serializer.is_a?(String) ? serializer.constantize : serializer
       end
 
-      attr_reader :name, :embed_ids, :embed_objects
+      attr_reader :name, :embed_ids, :embed_objects, :polymorphic
       attr_accessor :embed_in_root, :embed_key, :key, :embedded_key, :root_key, :serializer_from_options, :options, :key_format, :embed_in_root_key, :embed_namespace
       alias embed_ids? embed_ids
       alias embed_objects? embed_objects
       alias embed_in_root? embed_in_root
       alias embed_in_root_key? embed_in_root_key
       alias embed_namespace? embed_namespace
+      alias polymorphic? polymorphic
 
       def embed=(embed)
         @embed_ids     = embed == :id || embed == :ids