c++ - 为什么当我输入一个字符时我的程序有一个无限循环？

Question

#include<iostream>
#include<cstdlib>
#include<ctime>
#include<string>

using namespace std;

int main()
{
    char replay;
    int userInput;
    cout<< "Let's play Rock, Paper, Scissors"<<endl;
  do
 { 
    cout<<"Enter 1 for Rock, 2 for Paper, 3 for Scissors"<< endl;
    cin>> userInput;

    switch(userInput)
    {
      case 1:
      cout <<"You chose rock" << endl;
      break;

      case 2:
      cout <<"You chose paper" <<endl;
      break;

      case 3:
      cout <<"You chose scissors" << endl;
      break;

      default:
      cout << userInput << " is not a valid choice"<< endl;
      break;
   }  
    cout<<"Would you like to play again (Y for yes, N for no)?"<<endl;
    cin >> replay;
 }  while((replay=='Y') || (replay=='y')); 

    return 0; 

 }

当我在输入数字的答案中输入一个字符时，当我被问及是否要再次玩游戏时，我输入了一个不是 Y、y、N 或 n 的字符，它会进入无限循环

Answer 1

userInput 定义为 int。当您尝试读取一个 int，而流中实际是一个 char 时，它将失败(但 char 仍在缓冲区)。您必须清除错误状态并忽略错误输入:

if (!(cin >> userInput))
{
    cin.clear(); // clears the error state
    cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n'); // remove the bad input from the buffer
}
else
{
    // the code if the input was valid
}