操纵字符串成1个字符

Manipulating string into taking in 1 character

本文关键字：字符 1个字符串操纵更新时间：2023-10-16

我知道我的方法可能有点尴尬，我正在尝试验证菜单的输入，以便输入1-6之间的数字，而没有其他任何东西。我有工作代码，在其中将输入作为字符串进行输入，然后将其更改为INT以便在开关情况下使用它，但是我知道我可以使其更有效地工作。有什么想法吗？

 void menu(double pi, char ssTwo)                                                           //menu for choosing a shape
{
    string choice;
    cout << "Welcome to the shape calculator!nnPlease select what you wish to calculate:nn1 - Area of a Circlenn2 - Circumference of a Circlenn3 - Area of a Rectanglenn4 - Area of a Trianglenn5 - Volume of a Cuboidnn6 - Exit the programnn ";
    cin >> choice;
    while (choice != "1" && choice != "2" && choice != "3" && choice != "4" && choice != "5" && choice != "6")
    {
        cout << "Invalid input, please enter a number of 1-6nn";
        cin >> choice;
        cin.clear();
        cin.ignore(numeric_limits<streamsize>::max(), 'n');
    }
    int choiceInt = atoi(choice.c_str());
    system("CLS"); 
    switch (choiceInt)                                                          //switch case for each shape
    {
    case 1:
        circleArea(pi, ssTwo);
        break;
    case 2:
        circleCircum(pi, ssTwo);
        break;
    case 3:
        rectanArea(ssTwo);
        break;
    case 4:
        triangArea(ssTwo);
        break;
    case 5:
        cubVol();
        break;
    case 6:
        exitSystem();
        break;
    default:
        cout << "Invalid input, please enter a number of 1-5nn";
        menu(pi, ssTwo);
        break;
    }
}

将char视为ASCII值；检查http://rextester.com/xkmj90988

#define ONE 49
#define TWO 50
int main()
{
    char val = '1';
    switch (val)
    {
        case ONE:
        {
            std::cout << "1 was Selected";
            break;
        }
        case TWO :
        {
            std::cout << "2 was Selected";
            break;
        }   
        default:
            std::cout << "Invalid input, please enter a number of 1-5nn";
            break;
    }
}

更新＃1

检查：http：//rextester.com/wwum1166

，如果您将CIN的值读取到字符中而不是字符串，它只会采用第一个字符；因此，如果用户按" 1ASDFAD"，您将只有1个字符，并且将使用1个；如果按下" asdfasdf"，它将读取" a"，并显示无效的输入；

int main()
{
    char val;
    std::cout << "Enter a number: ";
    std::cin >> val;
    std::cout << val << "n";
    switch (val)
    {
        case '1':
        {
            std::cout << "1 was Selected";
            break;
        }
        case '2':
        {
            std::cout << "2 was Selected";
            break;
        }   
        default:
            std::cout << "Invalid input, please enter a number of 1-5nn";
            break;
    }
}