Adds the ability to decorate an enumerable proxy

lib/draper/decorated_enumerable_proxy.rb

@@ -4,6 +4,24 @@ class DecoratedEnumerableProxy
     include Enumerable
 
     delegate :as_json, :collect, :map, :each, :[], :all?, :include?, :first, :last, :shift, :to => :decorated_collection
+
+
+
+    # Initialize a new collection decorator instance by passing in
+    # an instance of a collection. Pass in an optional
+    # context into the options hash is stored for later use.
+    #
+    #
+    # @param [Object] instances to wrap
+    # @param [Hash] options (optional)
+    # @option options [Class] :klass The decorator class to use 
+    #   for each item in the collection.
+    # @option options all other options are passed to Decorator
+    #   class for each item.
+
+    def self.decorate(collection, options = {})
+      new( collection, discern_class_from_my_class(options.delete(:klass)), options)
+    end
 
     def initialize(collection, klass, options = {})
       @wrapped_collection, @klass, @options = collection, klass, options
@@ -70,5 +88,15 @@ def source
       @wrapped_collection
     end
     alias_method :to_source, :source
+
+
+    private
+    def self.discern_class_from_my_class default_class
+      return default_class if default_class
+      name = InvoiceDecorator.to_s.gsub("Decorator", "")
+      "#{name.singularize}Decorator".constantize
+    rescue NameError
+      raise NameError("You must supply a class (as the klass option) for the members of your collection or the class must be inferable from the name of this class ('#{new.class}')")
+    end
   end
 end