C++ 输入检查

Question

我有这段代码，它会进行输入检查。它工作到某个时候，但是当我输入例如应该无效的“12rc”时，检查被跳过。我该如何改变它？提前致谢!

cout << "Enter your choice 1, 2, 3: ";
cin >> choice;
cout << endl;
while (cin.fail() || choice <=0 || choice >=4) {  // check input value
    cin.clear();
    cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
    cout << "Wrong input value! Please enter only 1, 2, 3: ";
    cin >> choice;
    cout << endl;

Answer 1

我假设您想从标准输入流中获取一个整数。在其他情况下，您可能会采用相同的想法并意识到如何概括您的问题。 我认为它可能会像这样以某种方式解决

#include <iostream>
#include <cctype>
#include <stdexcept>

void skip_to_int() {
    if (std::cin.fail()) {
      // try to fix up a mess in the input
      std::cin.clear();

      for (char ch; std::cin >> ch; ) {
        if (std::isdigit(ch) || ch == '-') {
            std::cin.unget()
            return;
        }
      }
    }

    // throw an error for example
    throw std::invalid_argument{"Not integral input"};
}

int get_int() {
  int n;

  // try to get the integer number
  while (true) {
    if (std::cin >> n) {
      return n;
    }

    std::cout << "Sorry, that was not a number. Try again" << std::endl;
    // if user inputed not an integral try to search through stream for
    // int occurence
    skip_to_int();
  }
}

int main() {
  std::cout << "Enter your choice 1, 2, 3: " << std::endl;

  int choice = get_int(); 
  while (choice <= 0 && choice >= 3) {
    // continue searching
    choice = get_int();
  }

  // process choice somehow
}