import语句前面的下划线是什么意思? [英] What does an underscore in front of an import statement mean?

问题描述

我在sqlite3上看到了此示例c1> :

import (
        "database/sql"
        "fmt"
        _ "github.com/mattn/go-sqlite3"
        "log"
        "os"
)

并且似乎无法找到import语句前面的下划线是什么意思.

and cannot seem to find what the underscore in front of an import statement means.

推荐答案

简短答案:

仅出于副作用导入软件包.

Short answer:

It's for importing a package solely for its side-effects.

来自 Go规范:

要仅出于副作用(初始化)导入软件包，请使用空白标识符作为显式软件包名称:

To import a package solely for its side-effects (initialization), use the blank identifier as explicit package name:

导入_"lib/math"

import _ "lib/math"

在sqlite3中

对于 go-sqlite3 ，下划线import用于将sqlite3驱动程序注册为init()函数中的数据库驱动程序的副作用，而无需导入任何其他功能:

In sqlite3

In the case of go-sqlite3, the underscore import is used for the side-effect of registering the sqlite3 driver as a database driver in the init() function, without importing any other functions:

sql.Register("sqlite3", &SQLiteDriver{})

以这种方式注册后，sqlite3可以与代码中标准库的sql接口一起使用，如示例所示:

Once it's registered in this way, sqlite3 can be used with the standard library's sql interface in your code like in the example:

db, err := sql.Open("sqlite3", "./foo.db")

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