alias_method_makes_copy.rb

require 'forwardable'

class X
  def foo
    puts "foo!"
  end
  alias_method :bar, :foo
end

class Y < X
  def foo
    puts "foo! in Y"
  end
end

# alias_method makes a copy of the aliased method, so:
Y.new.foo # => foo! in Y
Y.new.bar # => foo!
puts "#" * 20

class A
  extend Forwardable
  def foo
    puts "foo!"
  end
  def_delegator :self, :foo, :bar
end

class B < A
  def foo
    puts "foo! in B"
  end
end

# def_delegator just forwards calls to the last argument to first.second
B.new.foo # foo! in B
B.new.bar # foo! in B