Dynamically alias methods and add functionality onto the end of them. Great for creating methods in rails that call `save!`.

alias_methodizer.rb

module AliasMethodizer
  private

  def alias_method(alias_name, name, &function)
    define_method alias_name, -> (*args, &block) do
      value = method(name)[*args, &block]
      instance_exec &function if block_given?
      value
    end
  end
end

class Foo
  extend AliasMethodizer

  def bar(x, y)
    p yield + x + y
  end

  def foo(x, y, &block)
    r = x + y
    block.call(r)
  end
  alias_method(:foo!, :foo) { bar(2, 3) { 1 } }
end

puts 'original'
p Foo.new.foo(1, 2) { |r| p r }

puts 'aliasized'
p Foo.new.foo!(1, 2) { |r| p r }