如何在 Go 中的 fmt.Scanf() 之后刷新 Stdin? [英] How to flush Stdin after fmt.Scanf() in Go?

问题描述

目前有一个问题困扰着我.当从用户那里获取输入时，我想使用一个循环来要求用户重试，直到他们输入有效的输入:

Here's an issue that's bedeviling me at the moment. When getting input from the user, I want to employ a loop to ask the user to retry until they enter valid input:

// user_input.go
package main

import (
    "fmt"
)

func main() {
    fmt.Println("Please enter an integer: ")

    var userI int

    for {
        _, err := fmt.Scanf("%d", &userI)
        if err == nil {
            break
        }
        fmt.Println("Sorry, invalid input. Please enter an integer: ")
    }

    fmt.Println(userI)    
}

运行上面的，如果用户输入有效，没问题:

Running the above, if the user enters valid input, no problem:

请输入一个整数:
3

3
退出代码 0，进程正常退出.

但是尝试输入一个字符串呢?

But try inputting a string instead?

请输入一个整数:什么?
抱歉，输入无效.请输入一个整数:
抱歉，输入无效.请输入一个整数:
对不起...

等等，它会一个字符一个字符地循环，直到字符串用完.即使输入单个字符循环两次，我也假设它解析换行符.

Etc, and it keeps looping character by character until the string is exhausted. Even inputting a single character loops twice, I assume as it parses the newline.

无论如何，一定有办法在 Go 中刷新 Stdin 吗?

Anyways, there must be a way to flush Stdin in Go?

附言如果没有这样的功能，您将如何解决它以提供等效的功能?我什至失败了...

P.S. In the absence of such a feature, how would you work around it to provide equivalent functionality? I've failed even at that...

推荐答案

我会在每次失败后通过阅读直到行尾来解决这个问题.这将清除文本的其余部分.

I would fix this by reading until the end of the line after each failure. This clears the rest of the text.

package main

import (
    "bufio"
    "fmt"
    "os"
)

func main() {
    stdin := bufio.NewReader(os.Stdin)

    fmt.Println("Please enter an integer: ")

    var userI int

    for {
        _, err := fmt.Fscan(stdin, &userI)
        if err == nil {
            break
        }

        stdin.ReadString('\n')
        fmt.Println("Sorry, invalid input. Please enter an integer: ")
    }

    fmt.Println(userI)
}

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