Document and add spec for delegating to constants in Forwardable

Fixes [Bug #13142]

1 files changed, 8 insertions, 2 deletions

diff --git a/lib/forwardable.rb b/lib/forwardable.rb
index f5202f9318..91c932913e 100644
--- a/lib/forwardable.rb
+++ b/lib/forwardable.rb
@@ -122,7 +122,8 @@ module Forwardable
   end
 
   # Takes a hash as its argument.  The key is a symbol or an array of
-  # symbols.  These symbols correspond to method names.  The value is
+  # symbols.  These symbols correspond to method names, instance variable
+  # names, or constant names (see def_delegator).  The value is
   # the accessor to which the methods will be delegated.
   #
   # :call-seq:
@@ -160,9 +161,12 @@ module Forwardable
 
   # Define +method+ as delegator instance method with an optional
   # alias name +ali+. Method calls to +ali+ will be delegated to
-  # +accessor.method+.
+  # +accessor.method+.  +accessor+ should be a method name, instance
+  # variable name, or constant name.  Use the full path to the
+  # constant if providing the constant name.
   #
   #   class MyQueue
+  #     CONST = 1
   #     extend Forwardable
   #     attr_reader :queue
   #     def initialize
@@ -170,12 +174,14 @@ module Forwardable
   #     end
   #
   #     def_delegator :@queue, :push, :mypush
+  #     def_delegator 'MyQueue::CONST', :to_i
   #   end
   #
   #   q = MyQueue.new
   #   q.mypush 42
   #   q.queue    #=> [42]
   #   q.push 23  #=> NoMethodError
+  #   q.to_i     #=> 1
   #
   def def_instance_delegator(accessor, method, ali = method)
     gen = Forwardable._delegator_method(self, accessor, method, ali)