search
HomeBackend DevelopmentGolangWhat is the use of the init() method in go language?
What is the use of the init() method in go language?Jan 07, 2023 pm 12:07 PM
golanggo languageinit()

In the Go language, the init() method is used for package initialization; after initializing each package, the init() function will be automatically executed, and the execution priority is higher than the execution priority of the main function. The init() method is usually used for: 1. Variable initialization; 2. Check/repair status; 3. Registrar; 4. Run calculations. The init() function is automatically called and executed when the program is running, and it cannot be actively called in the code. The init functions of different packages determine the execution order of the initialization functions according to the dependencies imported by the packages.

What is the use of the init() method in go language?

The operating environment of this tutorial: Windows 7 system, GO version 1.18, Dell G3 computer.

Detailed description of the Go init function

The init function in the go language is used to initialize the package (package). This function is of the go language. An important feature

When the program is executed, the import package statement will automatically trigger the call of the init() function inside the package.

After initializing each package, the init() function will be automatically executed, and the execution priority is higher than the execution priority of the main function.

It should be noted that the init() function has no parameters and no return value.

The init function is usually used for:

  • Variable initialization
  • Check/fix status
  • Registrar
  • Running calculation

#The init() function is automatically called and executed when the program is running, and it cannot be actively called in the code.

The sequence of package initialization execution is shown in the figure below:

What is the use of the init() method in go language?

The result is:

10
Hello 沙河

The init() function has the following characteristics:

  • The init function is a function used to initialize the package before program execution, such as initializing variables in the package, etc.

  • Each package can Having multiple init functions

  • Each source file of a package can also have multiple init functions

  • Multiple init functions in the same package The execution order of the go language has no clear definition (explanation)

  • The init functions of different packages determine the execution order of the initialization function according to the dependencies imported by the package

  • The init function cannot be called by other functions, but is automatically called before the main function is executed.

Package initialization

In order to use an imported package, it must first be initialized. Initialization is always performed in a single thread and in the order of package dependencies. This is controlled by Golang's runtime system, as shown below:

  • Initialize imported packages (recursive import)
  • Calculate and assign initial values ​​to variables declared in blocks
  • Execute the initialization function in the package

What is the use of the init() method in go language?

##initial.go

package main
import "fmt"
var _ int64=s()
func init(){
  fmt.Println("init function --->")
}
func s() int64{
  fmt.Println("function s() --->")
  return 1
}
func main(){
  fmt.Println("main --->")
}

Execution result

function s() —>
init function —>
main —>

Even if the package is imported multiple times, initialization only needs to be done once.

Feature introduction

The init function does not need to pass in parameters, nor does it need to return any value. In contrast to main, init is not declared and therefore cannot be referenced.

package main
import "fmt"
func init(){
  fmt.Println("init")
}
func main(){
  init()
}

An error occurred while compiling the above function "

undefined:init".

Each source file can contain more than one init function, please remember that the "way of march" written in each source file can only contain one init function, which is a bit different, so proceed to the next verification .

package main
import "fmt"
func init(){
  fmt.Println("init 1")
}
func init(){
  fmt.Println("init2")
}
func main(){
  fmt.Println("main")
}
/* 实施结果:
init1
init2
main */

From the above example, you can see that each source file can contain multiple init functions.

A common example of an initialization function is to set the value of an initial expression.

var precomputed=[20]float64{}
func init(){
  var current float64=1
  precomputed[0]=current
  for i:=1;i<len(precomputed);i++{
    precomputed[i]=precomputed[i-1]*1.2
  }
}

Because it is not possible to use a for loop as a precomputed value in the above code (which is a statement), you can use the init function to solve this problem.

Side effects of Go package import rules

Go is very strict and does not allow references to unused packages. But sometimes you reference the package just to call the init function to do some initialization. The purpose of the empty identifier (i.e. the underscore) is to solve this problem.

import _ "image/png"

【Related recommendations:

Go video tutorial, Programming teaching

The above is the detailed content of What is the use of the init() method in go language?. For more information, please follow other related articles on the PHP Chinese website!

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
go语言有没有缩进go语言有没有缩进Dec 01, 2022 pm 06:54 PM

go语言有缩进。在go语言中,缩进直接使用gofmt工具格式化即可(gofmt使用tab进行缩进);gofmt工具会以标准样式的缩进和垂直对齐方式对源代码进行格式化,甚至必要情况下注释也会重新格式化。

go语言为什么叫gogo语言为什么叫goNov 28, 2022 pm 06:19 PM

go语言叫go的原因:想表达这门语言的运行速度、开发速度、学习速度(develop)都像gopher一样快。gopher是一种生活在加拿大的小动物,go的吉祥物就是这个小动物,它的中文名叫做囊地鼠,它们最大的特点就是挖洞速度特别快,当然可能不止是挖洞啦。

一文详解Go中的并发【20 张动图演示】一文详解Go中的并发【20 张动图演示】Sep 08, 2022 am 10:48 AM

Go语言中各种并发模式看起来是怎样的?下面本篇文章就通过20 张动图为你演示 Go 并发,希望对大家有所帮助!

tidb是go语言么tidb是go语言么Dec 02, 2022 pm 06:24 PM

是,TiDB采用go语言编写。TiDB是一个分布式NewSQL数据库;它支持水平弹性扩展、ACID事务、标准SQL、MySQL语法和MySQL协议,具有数据强一致的高可用特性。TiDB架构中的PD储存了集群的元信息,如key在哪个TiKV节点;PD还负责集群的负载均衡以及数据分片等。PD通过内嵌etcd来支持数据分布和容错;PD采用go语言编写。

go语言能不能编译go语言能不能编译Dec 09, 2022 pm 06:20 PM

go语言能编译。Go语言是编译型的静态语言,是一门需要编译才能运行的编程语言。对Go语言程序进行编译的命令有两种:1、“go build”命令,可以将Go语言程序代码编译成二进制的可执行文件,但该二进制文件需要手动运行;2、“go run”命令,会在编译后直接运行Go语言程序,编译过程中会产生一个临时文件,但不会生成可执行文件。

【整理分享】一些GO面试题(附答案解析)【整理分享】一些GO面试题(附答案解析)Oct 25, 2022 am 10:45 AM

本篇文章给大家整理分享一些GO面试题集锦快答,希望对大家有所帮助!

go语言是否需要编译go语言是否需要编译Dec 01, 2022 pm 07:06 PM

go语言需要编译。Go语言是编译型的静态语言,是一门需要编译才能运行的编程语言,也就说Go语言程序在运行之前需要通过编译器生成二进制机器码(二进制的可执行文件),随后二进制文件才能在目标机器上运行。

golang map怎么删除元素golang map怎么删除元素Dec 08, 2022 pm 06:26 PM

删除map元素的两种方法:1、使用delete()函数从map中删除指定键值对,语法“delete(map, 键名)”;2、重新创建一个新的map对象,可以清空map中的所有元素,语法“var mapname map[keytype]valuetype”。

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

MinGW - Minimalist GNU for Windows

MinGW - Minimalist GNU for Windows

This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.

DVWA

DVWA

Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

Atom editor mac version download

Atom editor mac version download

The most popular open source editor

VSCode Windows 64-bit Download

VSCode Windows 64-bit Download

A free and powerful IDE editor launched by Microsoft

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools