c++ - 在使用 cin 请求 int 时如何有效地防止用户输入？

Question

这是我在这里发表的第一篇文章，我是编程/C++ 的新手(实际上才进入这个兔子洞几周)。我在 Microsoft Visual Studio 2017 中有这个测试项目，我正试图弄清楚如何在使用 cin 时完全防止用户输入。如果我要求一个 int，而我只想要一个 1 或一个 0，我希望绝对没有办法让某人在诸如 2 或 n 之类的东西中放置，或者在不正确和正确的响应之间放置空格，例如“n 1”。目前，我已经到了这样的地步，我似乎可以创建一个不需要的结果的唯一方法是，如果我首先输入一个正确的整数(0 或 1)，然后在后面跟一个空格和任何其他字符，这个模式可以在初始正确的字符(0 a 42 f 9130)等之后跟上无限数量的空格和字符。除了用更困惑的代码获得所需的结果之外，我想知道我是否只是遗漏了一些 -我还没有听说过的内置功能可以使这个过程更加高效。这是我为达到这一点而写的:

#include <iostream>
#include <string>
#include <climits>

using namespace std;

int trap;
int wrongNumber();

int numOnly() {
    while (cin.fail())
    {
        // Using someone else's code for this while statement to figure out how to not take a char input when using an int
        // Update: Turned this into a function to be called on whenever cin has a chance to fail because users don't listen.

        cin.clear(); // clear input buffer to restore cin to a usable state
        cin.ignore(INT_MAX, '\n'); // ignore last input
        system("CLS");
        cout << "----------------------------------" << endl;
        cout << "|  You can only enter a number.  |" << endl;
        cout << "| Would you like to pick a card? |" << endl;
        cout << "|  Type 1 for yes or 0 for no!   |" << endl;
        cout << "----------------------------------" << endl;
        cin >> trap;
    }
    if (trap != 1 && trap != 0) {
        system("CLS");
        wrongNumber();
    }
    return trap;
}

int wrongNumber() {

    // At least I made this fail-safe on my own!

    while (trap != 1 && trap != 0) {
        system("CLS");
        cout << "----------------------------------" << endl;
        cout << "|    That is not a 1 or a 0!     |" << endl;
        cout << "| Would you like to pick a card? |" << endl;
        cout << "|   Type 1 for yes or 0 for no!  |" << endl;
        cout << "----------------------------------" << endl;
        cin >> trap;
    }
    if (cin.fail()) {
        system("CLS");
        numOnly();
    }
    return trap;
}

int main() {

    cout << "----------------------------------" << endl;
    cout << "| Would you like to pick a card? |" << endl;
    cout << "|   Type 1 for yes or 0 for no!  |" << endl;
    cout << "----------------------------------" << endl;
    cin >> trap;

    while (cin.fail())
    {
        numOnly();
    }

    if (trap != 1 && trap != 0) {
        wrongNumber();
    }

Answer 1

我建议您不要使用整数来存储"is"或“否”的答案，而是使用字符串。通过这种方式，您可以使用 cin.fail() 、cin.ignore() 和 cin.clear() 为自己节省一些代码行:

 int main() {

    string trap;
    cout << "----------------------------------" << endl;
    cout << "| Would you like to pick a card? |" << endl;
    cout << "|   Type 1 for yes or 0 for no!  |" << endl;
    cout << "----------------------------------" << endl;
        cin>>trap;

        while (trap != "1" && trap != "0") { //You can make this while block into a function if you prefer
            cout << "----------------------------------" << endl;
            cout << "|    That is not a 1 or a 0!     |" << endl;
            cout << "| Would you like to pick a card? |" << endl;
            cout << "|   Type 1 for yes or 0 for no!  |" << endl;
            cout << "----------------------------------" << endl;
                cin>>trap;
        }
    return 0;
}

如果您必须使用整数，那么您应该查看this和 capturing characters without pressing enter .