chainmethods.rb

class ChainMethod
  def initialize(method_name, params = [], callbacks = {})
    @method_name = method_name
    @params = params.to_a
    @callbacks = callbacks
  end

  def call(base_object)
    # calling before_callback if passed
    @callbacks[:before_callback].call(@params, base_object) if @callbacks[:before_callback].is_a?(Proc)

    # main stuff
    result = if @params.last.is_a? Proc
      base_object.send(@method_name, *@params[0...-1], &@params.last)
    else
      base_object.send(@method_name, *@params.to_a)  
    end

    # calling after_callback
    @callbacks[:after_callback].call(@params, result) if @callbacks[:after_callback].is_a?(Proc)

    # returning value
    result
  end
end

class Object
  def chain_methods(chain)
    chain.inject(self) { |result, chain_method| chain_method.call(result) }
  end
end

callback_proc = Proc.new do |params, result|
  puts "params = #{params.inspect}"
  puts "result = #{result.inspect}"
end

p ["a", "b", "c"].chain_methods([
  ChainMethod.new("reverse"),
  ChainMethod.new("uniq"),
  ChainMethod.new("map", [proc{|x| x.upcase}], {:after_callback => callback_proc}),
  ChainMethod.new("map", [proc{|x| x.downcase}], {:before_callback => proc{ |params| p params}, :after_callback => callback_proc})
  ])

 result = if @params.last.is_a? Proc
      base_object.send(@method_name, *@params[0...-1], &@params.last)
    else
      base_object.send(@method_name, *@params.to_a)  
    end

красава!