reader of the Module calss in Ruby?

This question already has an answer here:

What is attr_accessor in Ruby? 18 answers

---

It works like this:

module Attr
  attr_accessor :my_variable
end

class MyClass
  @my_variable = "hi"
  def initialize
    @my_variable = "ho"
  end
end

You include the module in the class to construct an accessor for the instance variable @my_variable :

MyClass.include Attr
c = MyClass.new
c.my_variable                #=> "ho"
c.my_variable = "huh?"       #=> "huh?"
c.my_variable                #=> "huh?"

You extend the module to the class to construct an accessor for the class instance variable @my_variable :

MyClass.extend Attr          #=> MyClass
MyClass.my_variable          #=> "hi"
MyClass.my_variable = "nuts" #=> "nuts"
MyClass.my_variable          #=> "nuts"
c.my_variable                #=> "huh?"

As you see, the instance variable @my_variable is distinct from the class instance variable @my_variable . They coexist just as they would if they had different names.

More commonly, you'll see include and extend within the class definition, but the effect is the same as what I have above:

class MyClass
  include Attr
  extend Attr
  @my_variable = "hi"
  def initialize
    @my_variable = "ho"
  end
end

链接地址: http://www.djcxy.com/p/25774.html

上一篇: 在Rails中的访问器

下一篇: 读者在Ruby模块calss？