用户输入错误的输入时，从cin而不是一个字符中清除整行 [英] Clear entire line from cin instead of one character at a time when the user enters bad input

问题描述

我对cin的某些命令有疑问.我对C ++还是很陌生，所以请多多包涵.

I have a question on some commands for cin. I'm still very new to c++ so bear with me.

我正在做一个简单的计算程序，其中用户输入一个值，然后程序使用输入进行计算.我试图创建一个循环来检查输入，以确保用户输入的数字.经过一些研究，我发现使用 cin.clear 和 cin.ignore 会清除先前的输入，因此用户可以在循环检查后看是否没有输入新值.一个号码.效果很好，除非用户输入的单词大于1个字母.然后，它循环并一次删除每个字母，直到清除上一个cin.有没有办法删除整个单词，而不是一次删除一个字符?我觉得我误解了cin命令的实际作用.

I'm doing a simple calculation program where the user inputs a value and the program does a calculation with the input. I'm attempting to create a loop that checks the input to ensure the user inputted and number. After some research I found that using cin.clear and cin.ignore will clear the previous input so the user can input a new value after the loop checks to see if its not a number. It works well, except when the user inputs a word larger then 1 letter. It then loops and removes each letter one at a time until the previous cin is cleared. Is there a way to remove the entire word rather then one character at a time? I feel I have incorrectly interpreted what the cin commands actually do.

这是有问题的代码:

//Ask the user to input the base
cout << "Please enter the Base of the triangle" << endl;
cin >> base;

//A loop to ensure the user is entering a numarical value
while(!cin){

    //Clear the previous cin input to prevent a looping error
    cin.clear();
    cin.ignore();
    //Display command if input isn't a number 
        cout << "Not a number. Please enter the Base of the triangle" << endl;
        cin >> base;
}

推荐答案

我认为您可以在网上以多种方式获得答案.仍然对我有用:

I think you could get the answer in many ways on the net. Still this works for me:

#include <iostream>
#include <limits>

using namespace std;

int main() {
    double a;
    while (!(cin >> a)) {
        cin.clear();
        cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
        cout << "Wrong input, retry!" << endl;
    }
    cout << a;
}

此示例比注释中链接的示例更简单，因为您希望用户输入，每行一个输入.

This example is simpler than the one linked in the comments since you are expecting input from the user, one input per line.

这篇关于用户输入错误的输入时，从cin而不是一个字符中清除整行的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！