您如何限制C ++中用户输入的最大字符数？ [英] How do you limit the maximum amount of characters in user input in C++?

问题描述

我想要它，以便当用户输入超过5个字符时，会发生某些事情，而不仅仅是跳过其余字符。

I want it so that when the user inputs more than 5 characters, something will happen, instead of just skipping the rest.

在此代码中，如果您键入如果超过5个字符，则只会显示前5个字符。
我想在此处添加 if语句，如果用户输入的字符超过5个，它将显示错误或类似内容，而不仅仅是显示前5个字符。

In this code, if you type in more than 5 characters, it will only show the first 5 characters. I want to put an "if" statement here that if the user inputs more than 5 characters, it will show an error or something, and not just show the first 5 characters.

#include <iostream>
#include <iomanip>

int main()
{
using namespace std;
string nationname;
int maxchar = 5;
cout << "What is the name of your nation?\n";

cin >> setw(maxchar) >> nationname;

cout << "The name of your nation is " << nationname;
cin.ignore();

return 0;
}

谢谢！

推荐答案

您可以先完整读取字符串，然后验证它：

You could read the string in its entirety first and then validate it:

int main()
{
    using namespace std;

    const int maxchar = 5;
    string nationname;

    cout << "What is the name of your nation?" << endl;

    cin >> nationname;

    if (nationname.size() > maxchar)
    {
       err << "The input is too long." << endl;
       return 1;
    }

    // ...
}

顺便说一句，您应该在提示符下使用 std :: endl ，而不仅仅是 \n ；您想要确保在开始等待用户输入之前将提示刷新到屏幕上。 （编辑：正如Loki Astari在评论中指出的那样，这部分实际上不是必需的。）

Incidentally, you should use std::endl with your prompt and not just \n; you want to make sure that the prompt is flushed to the screen before you start waiting for user input. ( As Loki Astari points out in the comments, this part's not actually necessary.)

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