tweet pre-post condition contract

tweet contract thingy.rb

class Contract
  @@disable_override = false

  @@contracts = []

  def self.method_added name
    unless @@disable_override
      @@contracts.each do |method|
        if name == method.to_sym
          method_alias = "#{method}_alias".to_sym
          method_contract = "#{method}_contract".to_sym

          @@disable_override = true # to stop the new build method 
          self.send :alias_method, method_alias, name
          self.send :remove_method, name
          self.send :alias_method, name, method_contract

          @@disable_override = false
        else
          puts "defining other method #{name}"
        end
      end
    end
  end

end

class TweetGatewayContract < Contract

  @@contracts = [ 'save_tweet' ]

  def save_tweet_contract(foo)
    result = save_tweet_alias(foo)
    
    if result != "result: " + foo
      raise 'fail!'
    end
    return result
  end

end


class TG < TweetGatewayContract
  def save_tweet(foo)
    return "result: " + foo
  end
end

tg = TG.new
result = tg.save_tweet 'hi'
puts result