Question

我有一个while循环请求用户输入。在while while循环中我有一个switch语句。如何才能使其达到默认值，重复循环再次询问用户性别？

do
    {
        cout << "What is your weight?" << endl;
        cin >> weight;
        cout << "What is your height?" << endl;
        cin >> height;
        cout << "What is your age?" << endl;
        cin >> age;
        cout << "What is your gender?" << endl;
        cin >> gender;

        switch (gender)
        {
            case 'M':
            case 'm':
                cout << endl << Male(weight, height, age);
                break;
            case 'F':
            case 'f':
                cout << endl << Female(weight, height, age);
                break;
            default:
                cout << "What is your gender?";
        }

        cout << "Do you want to continue? (Y/N)" << endl;
        cin >> stopApp;

    } while(toupper(stopApp) == 'Y');

Answer 1

一个选项是设置一个布尔值，如果达到默认情况，则将其设置为true以重复。

bool repeat;
do {
  repeat = false;
  //switch statement
  switch {
    default:
      repeat = true;
  }
while(repeat);

你可以适当地使用重复来知道你想重复哪个问题。

Answer 2

此类事情的典型模式是循环，直到用户输入有效输入。 IE

    do {
        cout << "What is your weight?" << endl;
        cin >> weight;
        cout << "What is your height?" << endl;
        cin >> height;
        cout << "What is your age?" << endl;
        cin >> age;
        cout << "What is your gender?" << endl;
        cin >> gender;
    } while (!validGender(gender));

    // process valid input

虽然这并没有准确回答你的问题，但对于你想要做的事情来说，这是一个很好的模式。

Answer 3

由于break超载意味着“切换案例结束”和“退出循环”，这是goto合适的异常时期之一。

do
    {
    again:
        cout << "What is your weight?" << endl;
        cin >> weight;
        cout << "What is your height?" << endl;
        cin >> height;
        cout << "What is your age?" << endl;
        cin >> age;
        cout << "What is your gender?" << endl;
        cin >> gender;

        switch (gender)
        {
            case 'M':
            case 'm':
                cout << endl << Male(weight, height, age);
                break;
            case 'F':
            case 'f':
                cout << endl << Female(weight, height, age);
                break;
            default:
                cout << "What is your gender?";
                goto again;
        }

        cout << "Do you want to continue? (Y/N)" << endl;
        cin >> stopApp;

    } while(toupper(stopApp) == 'Y');

仅供参考“男性”和“女性”为not the only options for gender。根据你的更大目标，我建议你要么完全避免提出这个问题，允许用户提供任意的短语作为回应，或者，如果这是一个医疗应用，其中生物性是实际相关信息，请求相反（并再次允许提供任意短语，因为不是二进制）。

Answer 4

do
{
    cout << "What is your weight?" << endl;
    cin >> weight;
    cout << "What is your height?" << endl;
    cin >> height;
    cout << "What is your age?" << endl;
    cin >> age;

    bool repeat(true);
    do {
        cout << "What is your gender?" << endl;
        cin >> gender;

        switch (gender)
        {
            case 'M':
            case 'm':
                cout << endl << Male(weight, height, age);
                repeat = false;
                break;
            case 'F':
            case 'f':
                cout << endl << Female(weight, height, age);
                repeat = false;
                break;
            default:
                break;
        }
    } while(repeat)

    cout << "Do you want to continue? (Y/N)" << endl;
    cin >> stopApp;

} while(toupper(stopApp) == 'Y');

如果switch语句达到默认值，则重复执行while循环

4 个答案: