ruby 如何访问类变量？
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How do I access class variable?
提问by Vladislav Aniskin
class TestController < ApplicationController
def test
@goodbay = TestClass.varible
end
end
class TestClass
@@varible = "var"
end
and i get error
我得到错误
undefined method 'varible' for TestClass:Class
on the line @goodbay = TestClass.varible
在线上 @goodbay = TestClass.varible
What is wrong?
怎么了？
回答by Phrogz
In Ruby, reading and writing to @instancevariables (and @@classvariables) of an object must be done through a method on that object. For example:
在 Ruby 中，必须通过该对象上的方法来读取和写入对象的@instance变量（和@@class变量）。例如：
class TestClass
@@variable = "var"
def self.variable
# Return the value of this variable
@@variable
end
end
p TestClass.variable #=> "var"
Ruby has some built-in methods to create simple accessor methods for you. If you will use an instance variable on the class (instead of a class variable):
Ruby 有一些内置方法可以为您创建简单的访问器方法。如果您将在类上使用实例变量（而不是类变量）：
class TestClass
@variable = "var"
class << self
attr_accessor :variable
end
end
Ruby on Rails offers a convenience methodspecifically for class variables:
Ruby on Rails 提供了一种专门用于类变量的便捷方法：
class TestClass
mattr_accessor :variable
end
回答by Andrey Deineko
You have to access the class variable correctly. One of the ways is as follows:
您必须正确访问类变量。其中一种方法如下：
class TestClass
@@varible = "var"
class << self
def variable
@@varible
end
end
# above is the same as
# def self.variable
# @@variable
# end
end
TestClass.variable
#=> "var"
回答by zhu jiang
hava other method
有其他方法
class RubyList
@@geek = "Matz"
@@country = 'USA'
end
RubyList.class_variable_set(:@@geek, 'Matz rocks!')
puts RubyList.class_variable_get(:@@geek)
