go - 在 Go Lang 中导入自定义包时出错

Question

我创建了一个名为 libfastget 的库，该库位于 src 中，我的程序为

src
|-libfastget
|  |-libfastget.go
|
|-MainProgram
   |-main.go

libfastget 导出一个函数 fastget 如下

package libfastget

import (
    "fmt"
    "io"

)


func fastget(urlPtr *string, nPtr *int, outFilePtr *string) download {
    .....
    return dl

}

当我在主程序中使用库时

package main

import (
    "fmt"
    "net/http"
    "os"
    "libfastget"
    "path/filepath"
    "strings"
    "flag"
    "time"

)
func uploadFunc(w http.ResponseWriter, r *http.Request) {

         n:=libfastget.fastget(url,4,filename)

    }

}

我在尝试使用 go build 构建时遇到以下错误

# FServe
./main.go:94: cannot refer to unexported name libfastget.fastget
./main.go:94: undefined: libfastget.fastget

奇怪的是库文件 libfastget.a 存在于 pkg 文件夹中。

Answer 1

你需要让你的函数可以用大写的名字导出:

func Fastget(...

用作:

n:=libfastget.Fastget(url,4,filename)

规范提到:“Exported identifiers”:

An identifier may be exported to permit access to it from another package. An identifier is exported if both:

• the first character of the identifier's name is a Unicode upper case letter (Unicode class "Lu"); and
• the identifier is declared in the package block or it is a field name or method name.

All other identifiers are not exported.