オープンクラス

prepend インクルードしたクラスの下に挿入される

Refinements、using

第3章

def refresh(options={})
  defaults = {}
  attributes = [:input, :output, :commands, :print, :quiet,
                :exception_handler, :hooks]
  attributes.each do |attribute|
    defaults[attribute] = Pry.send attribute
  end
  # ...
  defaults.merge!(options).each do |key, value|
    send("#{key}=", value) if respond_to?("#{key}=")
  end

  true
end  

class MyClass
  define_method :my_method do |my_arg|
    my_arg * 3
  end
end

obj = MyClass.new
obj.my_method(2) # => 6

class Computer
  def initialize(computer_id, data_source)
    @id = computer_id
    @data_source = data_source
  end

  def self.define_component(name)
    define_method(name) do
      info = @data_source.send "get_#{name}_info", @id
      # price = ~~
      # result = ~~
      # return ~~
      # result
    end
  end

  define_component :mouse
  define_component :cpu
  define_component :keyboard
end

class Lawyer
  def method_missing(method, *args)
    puts "呼び出した : #{method}(#{args.join(', ')}"
    puts "ブロックも渡した" if block_given?
  end
end

class Computer
  def initialize(computer_id, data_source)
    @id = computer_id
    @data_source = data_source
  end

  def method_missing(name)
    super if !@data_source.respond_to?("get_#{name}_info")
    info = @data_source.send("get_#{name}_info", @id)
    # 省略
  end

  def respond_to_missing?(method, include_private = false)
    @data_source.respond_to?("get_#{method}_info") || super
  end
end