C++ 输入验证

Question

我正在开始 C++ 编程，必须进行大量输入验证。我发现这个功能似乎普遍适用，但有一个方面有问题；如果我输入 -90，程序不会报错。我的问题是:1、如何添加input不能<=0的情况？2.有没有更好的方法来限制用户输入？也许是 C++ 中的库？

感谢您的帮助或建议。

#include <ios>  // Provides ios_base::failure
#include <iostream>  // Provides cin

template <typename T>
T getValidatedInput()
{
    // Get input of type T
    T result;
    cin >> result;

    // Check if the failbit has been set, meaning the beginning of the input
    // was not type T. Also make sure the result is the only thing in the input
    // stream, otherwise things like 2b would be a valid int.
    if (cin.fail() || cin.get() != '\n')
    {
        // Set the error state flag back to goodbit. If you need to get the input
        // again (e.g. this is in a while loop), this is essential. Otherwise, the
        // failbit will stay set.
        cin.clear();

        // Clear the input stream using and empty while loop.
        while (cin.get() != '\n')
            ;

        // Throw an exception. Allows the caller to handle it any way you see fit
        // (exit, ask for input again, etc.)
        throw ios_base::failure("Invalid input.");
    }

    return result;
}

用法

inputtest.cpp

#include <cstdlib>  // Provides EXIT_SUCCESS
#include <iostream>  // Provides cout, cerr, endl

#include "input.h"  // Provides getValidatedInput<T>()

int main()
{
    using namespace std;

    int input;

    while (true)
    {
        cout << "Enter an integer: ";

        try
        {
            input = getValidatedInput<int>();
        }
        catch (exception e)
        {
            cerr << e.what() << endl;
            continue;
        }

        break;
    }

    cout << "You entered: " << input << endl;

    return EXIT_SUCCESS;
}

Answer 1

你可以使用函数来验证

template <typename T>
T getValidatedInput(function <bool(T)> validator) {
    T tmp;
    cin >> tmp;
    if (!validator(tmp)) {
        throw ios_base::failure("Invalid input.");
    }
    return tmp;
}

用法

int input = getValidatedInput<int>([] (int arg) -> bool {
    return arg >= 0;
});