Question

我试图检查无效的输入数据类型。如果输入数据类型是char类型，我想重新循环菜单选项。但我的程序终止了。

int menu()
{
    int choice = 15;
    while ((choice > 14) || ( choice < 0))
    {
        cout << "Enter 0 to quit\n";
        cout << "Enter 1 for Addition\n";
        cout << "Enter 2 for Subtraction\n";
        cout << "Enter 3 for Multiplication\n";
        cout << "Enter 4 for Division of two integers\n";
        cout << "Enter 5 for Real Division of two integers\n";
        cout << "Enter 6 for Quotient of a division\n";
        cout << "Enter 7 for Remainder of a division\n";
        cout << "Enter 8 for Factorial of an integer\n";
        cout << "Enter 9 for Exponential of two integers\n";
        cout << "Enter 10 for Finding if number is even or odd\n";
        cout << "Enter 11 for Area of a Square\n";
        cout << "Enter 12 for Area of a Circle\n";
        cout << "Enter 13 for Area of an Isoceles Triangle\n";
        cout << "Enter 14 for Converting Decimal to binary or hexadecimal\n";
        cin >> choice;

        if((choice > 14) || (choice < 0))
        {
            cout << "Invalid entry: Try again" << endl << endl;
        }
        else if ( !choice ) 
        {
            return choice;
        }
        else if (choice)
        {
            return choice;
        }
    }

    return choice;
}

Output after entering char 'f' as cin

Answer 1

试试这个

if (cin >> choice)
{
    if((choice > 14) || (choice < 0))
        cout << "Invalid entry: Try again" << endl << endl;
    else
        return choice;
}
else //Fail to cin into choice, user input is not a number
    cout << "Invalid entry: Please key in a number." << endl;

此外，while条件应更改为while (true)

Answer 2

删除空格行，然后再次运行代码。

if((choice > 14) || (choice < 0))
    cout << "Invalid entry: Try again" << endl << endl;

else if ( !choice ) 
{
 return choice;
}
////// remove the empty space line below///////////
else if (choice)
    return choice;
///////////////////////////////////////////////////

如何在无效数据类型输入后继续循环？

2 个答案: