variables - Go err : cannot use cur (type *user. User) 作为 f.WriteString 参数中的类型字符串

Question

如何将数据转换为 string 类型？我需要将我需要的数据写到不是变量的文件中，我该怎么做？

代码:

package main

import "os"
import "os/user"
import "encoding/json"

func main(){
    f, err := os.OpenFile("test.txt", os.O_APPEND|os.O_WRONLY, 0600)
    if err != nil {
        panic(err)
    }
    defer f.Close()

    cur, err := user.Current()
    if err != nil {

    } else {


        if _, err = f.WriteString(cur); err != nil {
        panic(err)
        }
    }
}

我不需要使用 cur.Username 字段。只是一个变量。

Answer 1

File.WriteString()需要一个 string 参数，但您尝试将 cur 传递给它，类型为 *user.User ，指向结构的指针。这显然是一个编译时错误。

user.User 是一个具有以下定义的结构体:

type User struct {
        // Uid is the user ID.
        // On POSIX systems, this is a decimal number representing the uid.
        // On Windows, this is a security identifier (SID) in a string format.
        // On Plan 9, this is the contents of /dev/user.
        Uid string
        // Gid is the primary group ID.
        // On POSIX systems, this is a decimal number representing the gid.
        // On Windows, this is a SID in a string format.
        // On Plan 9, this is the contents of /dev/user.
        Gid string
        // Username is the login name.
        Username string
        // Name is the user's real or display name.
        // It might be blank.
        // On POSIX systems, this is the first (or only) entry in the GECOS field
        // list.
        // On Windows, this is the user's display name.
        // On Plan 9, this is the contents of /dev/user.
        Name string
        // HomeDir is the path to the user's home directory (if they have one).
        HomeDir string
}

选择要输出到文件的内容，最有可能是 Username 字段或 Name 字段。这些是 string 类型的字段，因此您可以毫无问题地传递这些字段:

if _, err = f.WriteString(cur.Username); err != nil {
    panic(err)
}

如果你想写出完整的 User 结构，你可以使用 fmt包，方便fmt.Fprint()或 fmt.Fprintf()功能:

if _, err = fmt.Fprintf(f, "%+v", cur); err != nil {
    panic(err)
}