实例变量，类变量以及它们之间的区别(在ruby中) [英] instance variable, class variable and the difference between them in ruby

问题描述

我很难理解实例变量，类变量以及它们在ruby中的区别...有人可以向我解释它们吗?我已经做了大量的Google搜索，只是无法完全理解它们.

I am having a hard time understanding instance variable, class variable and the difference between them in ruby... can someone explain them to me? I have done tons of Google searches, just can't understand them fully.

谢谢！

推荐答案

假设您定义了一个类.一个类可以有零个或多个实例.

Let's say you define a class. A class can have zero or more instances.

class Post
end

p1 = Post.new
p2 = Post.new

实例变量的作用域是特定实例.这意味着，如果您有实例变量title，则每个帖子都会有自己的标题.

Instance variables are scoped within a specific instance. It means if you have an instance variable title, each post will have its own title.

class Post
  def initialize(title)
    @title = title
  end

  def title
    @title
  end
end

p1 = Post.new("First post")
p2 = Post.new("Second post")

p1.title
# => "First post"
p2.title
# => "Second post"

相反，在该类的所有实例之间共享一个类变量.

A class variable, instead, is shared across all instances of that class.

class Post
  @@blog = "The blog"

  def initialize(title)
    @title = title
  end

  def title
    @title
  end

  def blog
    @@blog
  end

  def blog=(value)
    @@blog = value
  end
end

p1 = Post.new("First post")
p2 = Post.new("Second post")

p1.title
# => "First post"
p2.title
# => "Second post"

p1.blog
# => "The blog"
p2.blog
# => "The blog"

p1.blog = "New blog"

p1.blog
# => "New blog"
p2.blog
# => "New blog"

这篇关于实例变量，类变量以及它们之间的区别(在ruby中)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！