define_method使用

定义方法

define_method :hello |country,city|
  puts "hello #{country}, I'm in #{city}"
end
hello('China' , 'XI\'AN') #=> hello China, I'm in XI'AN

简单模仿attr_accessor

class User
  def self.setup_accessor var
    define_method var do 
      instance_variable_get "＠#{var}" #获取实例变量
    end  
    define_method "#{var}=" do |value|
      instance_variable_set "＠#{var}", value
    end  
  end

  setup_accessor :name
  setup_accessor :age
end

user = User.new
user.name = "kakarot"
puts user.name #=> kakarot

模仿attr_accessor 进阶

class User

    def self.setup_accessor(*arg)
        arg.each do |var|
            define_method var do
                instance_variable_get "@#{var}"
            end
        end

        arg.each do |var|
            define_method "#{var}=" do |value| 
                instance_variable_set "@#{var}" ,value
            end
        end
    end

    setup_accessor :name, :age

end

user = User.new

user.name = "kakarot"
p user.name #=> "kakarot"

遍历＋define_method

class Myclass

    attr_reader :name,:age

    define_method :set_user do |name,age|
        @name = name
        @age = age
    end

    attributes = [:set_name, :set_age]

    attributes.each do |method_name,attribute|
        define_method method_name do |var|
            @name = var if method_name == :set_name
            @age = var if method_name == :set_age
        end
    end
end

obj = Myclass.new
obj.set_user("newton",43)
obj.send(:set_user,obj.name, 77)  
puts "user name is #{obj.name}, user age is #{obj.age}"


user = Myclass.new
user.set_name('kakarot')
user.set_age(43)
puts "user name is #{user.name}, user age is #{user.age}"