Add ArraySerializer's root and meta features

lib/active_model/array_serializer.rb

@@ -1,10 +1,23 @@
 module ActiveModel
   class ArraySerializer
-    def initialize(object, options={})
-      @object  = object
-      @options = options
+    class << self
+      attr_accessor :_root
+
+      def root(root)
+        @_root = root
+      end
+      alias root= root
     end
 
+    def initialize(object, options={})
+      @object   = object
+      @options  = options
+      @root     = options[:root] || self.class._root
+      @meta_key = options[:meta_key] || :meta
+      @meta     = options[@meta_key]
+    end
+    attr_accessor :object, :root, :meta_key, :meta
+
     def serializable_array
       @object.map do |item|
         serializer = @options[:each_serializer] || Serializer.serializer_for(item)
@@ -16,5 +29,15 @@ module ActiveModel
       end
     end
     alias serializable_object serializable_array
+
+    def as_json(options={})
+      if root = options[:root] || self.root
+        hash = { root.to_s => serializable_array }
+        hash[meta_key.to_s] = meta if meta
+        hash
+      else
+        serializable_array
+      end
+    end
   end
 end