c++ - 用户输入整数后跟垃圾

Question

在我的简单 Fraction类，我有以下方法来获取 numerator 的用户输入，它可以很好地检查像 garbage 这样的垃圾输入, 但不会识别以整数开头且后跟垃圾 1 garbage 的用户输入或 1garbage .

void Fraction::inputNumerator()
{
    int inputNumerator;

    // loop forever until the code hits a BREAK
    while (true) {
        std::cout << "Enter the numerator: ";

        // attempt to get the int value from standard input
        std::cin >> inputNumerator;

        // check to see if the input stream read the input as a number
        if (std::cin.good()) {

            numerator = inputNumerator;
            break;

        } else {

            // the input couldn't successfully be turned into a number, so the
            // characters that were in the buffer that couldn't convert are
            // still sitting there unprocessed.  We can read them as a string
            // and look for the "quit"

            // clear the error status of the standard input so we can read
            std::cin.clear();

            std::string str;
            std::cin >> str;

            // Break out of the loop if we see the string 'quit'
            if (str == "quit") {
                std::cout << "Goodbye!" << std::endl;
                exit(EXIT_SUCCESS);
            }

            // some other non-number string.  give error followed by newline
            std::cout << "Invalid input (type 'quit' to exit)" << std::endl;
        }
    }
}

我看到一些关于使用 getline 的帖子方法，但是当我尝试它们时它们没有编译，而且我找不到原始帖子，抱歉。

Answer 1

最好按如下方式检查:

// attempt to get the int value from standard input
if(std::cin >> inputNumerator)
{
    numerator = inputNumerator;
    break;
} else { // ...

或者是:按照建议解析一个完整的输入行，适本地组合 std::getline() 和 std::istringstream。