SimpleDelegator

        # SimpleDelegator < Delegator

(from ruby core)
---
A concrete implementation of Delegator, this class provides the means to
delegate all supported method calls to the object passed into the
constructor and even to change the object being delegated to at a later
time with #__setobj__.

    class User
      def born_on
        Date.new(1989, 9, 10)
      end
    end

    require 'delegate'

    class UserDecorator < SimpleDelegator
      def birth_year
        born_on.year
      end
    end

    decorated_user = UserDecorator.new(User.new)
    decorated_user.birth_year  #=> 1989
    decorated_user.__getobj__  #=> #<User: ...>

A SimpleDelegator instance can take advantage of the fact that
SimpleDelegator is a subclass of `Delegator` to call `super` to have
methods called on the object being delegated to.

    class SuperArray < SimpleDelegator
      def [](*args)
        super + 1
      end
    end

    SuperArray.new([1])[0]  #=> 2

Here's a simple example that takes advantage of the fact that
SimpleDelegator's delegation object can be changed at any time.

    class Stats
      def initialize
        @source = SimpleDelegator.new([])
      end

      def stats(records)
        @source.__setobj__(records)

        "Elements:  #{@source.size}\n" +
        " Non-Nil:  #{@source.compact.size}\n" +
        "  Unique:  #{@source.uniq.size}\n"
      end
    end

    s = Stats.new
    puts s.stats(%w{James Edward Gray II})
    puts
    puts s.stats([1, 2, 3, nil, 4, 5, 1, 2])

Prints:

    Elements:  4
     Non-Nil:  4
      Unique:  4

    Elements:  8
     Non-Nil:  7
      Unique:  6
---
# Instance methods:

    __getobj__
    __setobj__