From: "Jan E." <lists@...>
Date: 2013-01-04T11:46:18+09:00
Subject: Re: respond_to_missing?

Hi,

"respond_to_missing?" makes "respond_to?" fit for dynamic methods 
defined by "method_missing".

Normally, an object wouldn't know if it can respond to a dynamic method 
call:


#-----------------------
class A
  def method_missing name, *args
    if name == :say_hi
      puts 'Hi there!'
    else
      raise NoMethodError
    end
  end
end

a = A.new
a.say_hi                    # "Hi there!"
puts a.respond_to? :say_hi  # => false
#-----------------------


But if you define "respond_to_missing?", you can work around this 
problem:


#-----------------------
class A
  def method_missing name, *args
    if name == :say_hi
      puts 'Hi there!'
    else
      raise NoMethodError
    end
  end
  def respond_to_missing? name, include_private
    name == :say_hi
  end
end

a = A.new
a.say_hi                    # "Hi there!"
puts a.respond_to? :say_hi  # => true
#-----------------------

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