Go和Go =的区别是什么？ [英] What is the difference between := and = in Go?

问题描述

我是Go编程语言的新手。

我在Go中发现了一些奇怪的东西：我认为它使用了：= ，并用 = 在Python中，但是当我在Go中使用 = 时，它也是有效的。

：= 和 = ？

解决方案

= 是赋值。更多关于Go的分配：作业

当 = 时， = 和：= 之间的细微区别>在变量声明中使用。

Go中的变量声明的一般形式为：

  var name type = expression 
  

上面的声明创建了一个特定类型的变量，一个名称，并设置其初始值。 类型或 =表达式都可以省略，但不能同时存在。

例如：

  var x int = 1 
 var a int 
 var b，c，d = 3.14，stackoverflow，true 
  

：= 被称为短变量声明其形式为

  name：=表达式
  

并且名称的类型由表达式类型

请注意： ：= 是一个声明，而 = 是一项任务

所以，一个简短的变量声明必须至少声明至少一个新变量。这意味着一个简短的变量声明不一定会在其左侧声明所有的变量，当它们中的一些已经被声明在同一个词法块中时，那么：= 就像对这些变量赋值一样

例如：

  r ：= foo（）// ok，声明一个新变量r 
r，m：= bar（）// ok，声明一个新变量m并赋值ra新值
r，m：= bar2（） //编译错误：无新变量
  

另外，：= 可能只出现在函数内部。在某些情况下，例如if，for或switch语句的初始值设定项，它们可用于声明本地临时变量。

更多信息：

变量声明

短变量声明

I am new to Go programming language.

I noticed something strange in Go: I thought that it used := and substitutes = in Python, but when I use = in Go it is also works.

What is the difference between := and =?

解决方案

= is assignment. more about assignment in Go: Assignments

the subtly difference between = and := is when = used in variable declarations.

General form of variable declaration in Go is:

var name type = expression

the above declaration creates a variable of a particular type, attaches a name to it, and sets its initial value. Either the type or the = expression can be omitted, but not both.

For example:

var x int = 1
var a int
var b, c, d = 3.14, "stackoverflow", true

:= is called short variable declaration which takes form

name := expression

and the type of name is determined by the type of expression

Note that: := is a declaration, whereas = is an assignment

So, a short variable declaration must declare at least one new variable. which means a short variable declaration doesn't necessarily declare all the variables on its left-hand side, when some of them were already declared in the same lexical block, then := acts like an assignment to those variables

For example:

 r := foo()   // ok, declare a new variable r
 r, m := bar()   // ok, declare a new variable m and assign r a new value
 r, m := bar2()  //compile error: no new variables

Besides, := may appear only inside functions. In some contexts such as the initializers for "if", "for", or "switch" statements, they can be used to declare local temporary variables.

More info:

variable declarations

short variable declarations

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