From: George Ogata <george.ogata@...>
Date: 2007-01-31T20:48:45+09:00
Subject: Re: alias callback

On 1/30/07, Trans <transfire@gmail.com> wrote:
> How does one reflect on alias definitions. Using #method_added only
> gives you the name of the alias being defined --as if it were a new
> method. And it's not possible to override 'alias' b/c it's not a real
> method.
>
> Ideas?

UnboundMethod#== returns true for aliases, so hopefully:

  class Module
    def alias?(name)
      name = name.to_s
      instance_method = instance_method(name)
      (instance_methods + private_instance_methods).any? do |n|
        n != name && instance_method(n) == instance_method
      end
    end
  end

Bit of a test:

  require 'test/unit'
  class AliasTest < Test::Unit::TestCase
    def test_by_alias
      klass = Class.new do
        def foo
        end
        def bar
        end
        alias baz foo
      end
      assert  klass.alias?(:foo)
      assert !klass.alias?(:bar)
      assert  klass.alias?(:baz)
    end
    def test_by_alias_method
      klass = Class.new do
        def foo
        end
        def bar
        end
        alias_method :baz, :foo
      end
      assert  klass.alias?(:foo)
      assert !klass.alias?(:bar)
      assert  klass.alias?(:baz)
    end
    def test_across_inheritance
      klass = Class.new{alias foo object_id}
      assert klass.alias?(:foo)
      assert klass.alias?(:object_id)
    end
    def test_nonalias
      klass = Class.new{def foo; end}
      assert !klass.alias?(:foo)
    end
    def test_builtin
      assert  Array.alias?(:size)
      assert  Array.alias?(:length)
      assert !Array.alias?(:clear)
    end
  end