2 files changed, 159 insertions, 0 deletions
diff --git a/activemodel/lib/active_model.rb b/activemodel/lib/active_model.rb
index d0e2a6f39c..28765b00bb 100644
--- a/activemodel/lib/active_model.rb
+++ b/activemodel/lib/active_model.rb
@@ -43,6 +43,7 @@ module ActiveModel
   autoload :Observer, 'active_model/observing'
   autoload :Observing
   autoload :SecurePassword
+  autoload :Serializer
   autoload :Serialization
   autoload :TestCase
   autoload :Translation
diff --git a/activemodel/lib/active_model/serializer.rb b/activemodel/lib/active_model/serializer.rb
new file mode 100644
index 0000000000..6d0746a3e8
--- /dev/null
+++ b/activemodel/lib/active_model/serializer.rb
@@ -0,0 +1,158 @@
+require "active_support/core_ext/class/attribute"
+require "active_support/core_ext/string/inflections"
+require "active_support/core_ext/module/anonymous"
+require "set"
+
+module ActiveModel
+  class Serializer
+    module Associations
+      class Config < Struct.new(:name, :options)
+        def serializer
+          options[:serializer]
+        end
+      end
+
+      class HasMany < Config
+        def serialize(collection, scope)
+          collection.map do |item|
+            serializer.new(item, scope).serializable_hash
+          end
+        end
+
+        def serialize_ids(collection, scope)
+          # use named scopes if they are present
+          #return collection.ids if collection.respond_to?(:ids)
+
+          collection.map do |item|
+            item.read_attribute_for_serialization(:id)
+          end
+        end
+      end
+
+      class HasOne < Config
+        def serialize(object, scope)
+          object && serializer.new(object, scope).serializable_hash
+        end
+
+        def serialize_ids(object, scope)
+          object && object.read_attribute_for_serialization(:id)
+        end
+      end
+    end
+
+    class_attribute :_attributes
+    self._attributes = Set.new
+
+    class_attribute :_associations
+    self._associations = []
+
+    class_attribute :_root
+    class_attribute :_embed
+    self._embed = :objects
+    class_attribute :_root_embed
+
+    class << self
+      def attributes(*attrs)
+        self._attributes += attrs
+      end
+
+      def associate(klass, attrs)
+        options = attrs.extract_options!
+        self._associations += attrs.map do |attr|
+          unless method_defined?(attr)
+            class_eval "def #{attr}() object.#{attr} end", __FILE__, __LINE__
+          end
+
+          options[:serializer] ||= const_get("#{attr.to_s.camelize}Serializer")
+          klass.new(attr, options)
+        end
+      end
+
+      def has_many(*attrs)
+        associate(Associations::HasMany, attrs)
+      end
+
+      def has_one(*attrs)
+        associate(Associations::HasOne, attrs)
+      end
+
+      def embed(type, options={})
+        self._embed = type
+        self._root_embed = true if options[:include]
+      end
+
+      def root(name)
+        self._root = name
+      end
+
+      def inherited(klass)
+        return if klass.anonymous?
+
+        name = klass.name.demodulize.underscore.sub(/_serializer$/, '')
+
+        klass.class_eval do
+          alias_method name.to_sym, :object
+          root name.to_sym unless self._root == false
+        end
+      end
+    end
+
+    attr_reader :object, :scope
+
+    def initialize(object, scope)
+      @object, @scope = object, scope
+    end
+
+    def as_json(*)
+      if _root
+        hash = { _root => serializable_hash }
+        hash.merge!(associations) if _root_embed
+        hash
+      else
+        serializable_hash
+      end
+    end
+
+    def serializable_hash
+      if _embed == :ids
+        attributes.merge(association_ids)
+      elsif _embed == :objects
+        attributes.merge(associations)
+      else
+        attributes
+      end
+    end
+
+    def associations
+      hash = {}
+
+      _associations.each do |association|
+        associated_object = send(association.name)
+        hash[association.name] = association.serialize(associated_object, scope)
+      end
+
+      hash
+    end
+
+    def association_ids
+      hash = {}
+
+      _associations.each do |association|
+        associated_object = send(association.name)
+        hash[association.name] = association.serialize_ids(associated_object, scope)
+      end
+
+      hash
+    end
+
+    def attributes
+      hash = {}
+
+      _attributes.each do |name|
+        hash[name] = @object.read_attribute_for_serialization(name)
+      end
+
+      hash
+    end
+  end
+end