How do package visibility rules work in Golang?

Package visibility rules in Go determine whether an identifier is accessible outside the package. Exported identifiers start with an uppercase letter and are accessible from the outside, while identifiers that start with a lowercase letter are private and can only be accessed within the package in which they are defined. Exported identifiers allow use in other packages, while private identifiers encapsulate implementation details and prevent accidental use.

Package visibility rules in Go

In the Go language, package visibility rules determine the identity of the package When symbols (variables, types, constants, functions, etc.) can be accessed outside the package. Understanding these rules is crucial to writing modular and maintainable Go code.

Exported identifiers

Exported identifiers begin with a capital letter. To access an identifier from outside the package, it must be exported. Exporting identifiers allows users to use them in other packages and document them in the package documentation (godoc).

package mypkg

// 导出的变量
var ExportedVariable = 10

// 导出的类型
type ExportedType struct {
    Field1 string
    Field2 int
}

Private identifiers

Identifiers starting with a lowercase letter are private. They are only accessible within the package in which they are defined. Private identifiers are used to encapsulate internal implementation details of a package and prevent their accidental use in other packages.

package mypkg

// 私有变量
var privateVariable = 20

// 私有类型
type privateType struct {
    Field1 bool
    Field2 string
}

Practical case

Consider a package called myutils, which provides some useful utility functions. To make these functions available outside the package, they must be exported:

package myutils

// 导出函数
func ExportFunction() {
    // 函数逻辑
}

You can then import the myutils package in another package and use the exported functions:

package main

import "myutils"

func main() {
    myutils.ExportFunction()
}

Note:

• The package name must be lowercase.
• There are no access control keywords (such as public, private, protected) in Go. Package visibility rules determine access permissions for identifiers.
• Export identifiers should be used with caution because they affect the external interface of the package.
• Private identifiers can improve code encapsulation and reduce accidental use.

The above is the detailed content of How do package visibility rules work in Golang?. For more information, please follow other related articles on the PHP Chinese website!