:: 和 . 之间有区别吗?在 Ruby 中调用类方法时? [英] Is there a difference between :: and . when calling class methods in Ruby?

问题描述

一个简单的问题，但我一直很好奇……以下两个命令之间是否存在功能差异?

Simple question, but one that I've been curious about...is there a functional difference between the following two commands?

String::class
String.class

他们都按照我的期望去做——也就是说他们返回Class——但是使用::和有什么区别.?

They both do what I expect -- that is to say they return Class -- but what is the difference between using the :: and the .?

我注意到在那些定义了常量的类上，当您在 :: 之后而不是在 之后按 Tab 键时，IRB 的自动补全会将常量作为可用选项返回.，但我不知道这是什么原因...

I notice that on those classes that have constants defined, IRB's auto-completion will return the constants as available options when you press tab after :: but not after ., but I don't know what the reason for this is...

推荐答案

. 操作符基本上是说将此消息发送给对象".在您的示例中，它正在调用该特定成员.:: 运算符向下钻取"到运算符左侧定义的范围，然后调用运算符右侧定义的成员.

The . operator basically says "send this message to the object". In your example it is calling that particular member. The :: operator "drills down" to the scope defined to the left of the operator, and then calls the member defined on the right side of operator.

当您使用 :: 时，您必须引用已定义的成员.使用 . 时，您只是向对象发送消息.因为该消息可以是任何内容，所以自动完成对 . 不起作用，而对 :: 起作用.

When you use :: you have to be referencing members that are defined. When using . you are simply sending a message to the object. Because that message could be anything, auto-completion does not work for . while it does for ::.

这篇关于:: 和 . 之间有区别吗?在 Ruby 中调用类方法时?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！