cin >> int 给定一个字符串将 int 分配给 0

Question

我遇到的问题是，如果您输入任何字符串，cin 会将 int 分配为 0。一个有趣的发现是，如果您稍后将 cin 带入一个字符串，您将获得您为 int 输入的整个字符串.由于某种原因，cin.fail() 总是返回 true，即使使用 cin.ignore() 等，并且 if(cin >> startingPosition) 也总是返回 true。那么，我如何让它甚至识别出它是一个字符串而不是一个 int 呢？如，如果它是一个字符串，我如何让它再次循环？

int getUserPosition(bool volatileCall = false) {
    cout << "Which slot do you want to drop the chip in (0-8)? " << endl;
    int startingPosition;
    cin >> startingPosition;
    while (startingPosition >= WIDTH || startingPosition < 0) {
    cout << "Invalid slot." << endl << endl;

        if (volatileCall) {
            return -1;
        }
        cout << "Which slot do you want to drop the chip in (0-8)? " << endl;
        cin >> startingPosition;
        cout << startingPosition << endl;

    }
    return startingPosition;
}

Answer 1

你必须保存来自 cin 的结果

isNumber = (cin >> startPosition);

整个代码看起来像

int getUserPosition(bool volatileCall = false) {
    cout << "Which slot do you want to drop the chip in (0-8)? " << endl;
    int startingPosition;
    bool isNumber = (cin >> startingPosition);
    while(isNumber && (startingPosition >= WIDTH || startingPosition < 0)) {
        cout << "Invalid slot." << endl << endl;
        if (volatileCall) {
            return -1;
        }
        cout << "Which slot do you want to drop the chip in (0-8)? " << endl;
        isNumber = (cin >> startingPosition);
        cout << startingPosition << endl;
    }
    return startingPosition;
}