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c++ - 如何让用户在菜单选择中重新输入输入？

问题描述

我正在尝试创建一个菜单，让用户再试一次，直到他们输入一个有效的选择（1-5）。如果用户输入其他内容，我希望它显示错误消息并继续让他们重试。显然我的问题出在我的 while 循环中，但我不确定如何解决这个错误。有人可以帮我重组这段代码吗，谢谢。

#include <cstdlib>
#include <iostream>

using namespace std;

void myList() {
    char selection;
    cout << "\n Select Equipments by category for more details";
    cout << "\n====================================================";
    cout << "\n 1 - Gardening Equipment";
    cout << "\n 2 - Building Equipment";
    cout << "\n 3 - Decorating Equipment";
    cout << "\n 4 - Car Maintenance Equipment";
    cout << "\n 5 - Miscellaneous";
    cout << "\n X - Exit";
    cout << "\n Enter selection: ";

    // read the input
    cin >> selection;
    while((selection != 1) || (selection != 2) || (selection != 3) ||
          (selection != 4) || (selection != 5)) {
        cout << "ERROR: Invalid Key - Try Again: ";
        cin >> selection;
        cout << endl;
        switch(selection)
        {
        case '1':
            system("CLS");
            cout << " [GARDENING EQUIPMENT]" << endl
                 << " 1.Hoe" << endl
                 << " 2.Spade" << endl
                 << " 3.Fork" << endl
                 << " 4.Shovel" << endl
                 << " 5.Rake" << endl
                 << " 6.Saw" << endl
                 << " 7.Wheelbarrow" << endl;
            break;
        case '2':
            system("CLS");
            cout << " [BUILDING EQUIPMENT]" << endl
                 << " 1.Rammer" << endl
                 << " 2.Crowbar" << endl
                 << " 3.Cordless Drill" << endl
                 << " 4.Safety Helmet" << endl
                 << " 5.Safety Glass" << endl
                 << " 6.Spirit Level" << endl
                 << " 7.Concrete Mixer" << endl;
            break;
        case '3':
            system("CLS");
            cout << " [DECORATING EQUIPMENT]" << endl
                 << " 1.Wallpaper Strippers" << endl
                 << " 2.Paint rollers" << endl
                 << " 3.Protective Sheets" << endl
                 << " 4.Paint Trays" << endl
                 << " 5.Step Ladder" << endl
                 << " 6.Paint Conditioner" << endl
                 << " 7.Stanley Knife" << endl;
            break;
        case '4':
            system("CLS");
            cout << " [CAR MAINTENANCE EQUIPMENT]" << endl
                 << " 1.Extension Bar" << endl
                 << " 2.Spark Plug Pilers" << endl
                 << " 3.Air Compressor" << endl
                 << " 4.Oil drain & caddy" << endl
                 << " 5.Engine Hoist" << endl
                 << " 6.Brake lathe" << endl
                 << " 7.Transmission Jack" << endl;
            break;
        case '5':
            system("CLS");
            cout << " [MISCELLANEOUS]" << endl
                 << " 1.Cleaning Powder" << endl
                 << " 2.Aluminium Foil" << endl
                 << " 3.Filter Paper" << endl
                 << " 4.Nylon Scrubber" << endl
                 << " 5.Floor Duster" << endl
                 << " 6.Dettol" << endl
                 << " 7.Disposable Garbage Bag" << endl;
            break;
        case 'X':
        case 'x': {
            cout << "\n To exit the menu";
        }
        break;
            // other than A, M, D and X...
        default:
            cout << "\n Invalid selection";
            // no break in the default case
        }
        cout << "\n";
    }
}

int main()
{
    myList();
    return 0;
}

标签： c++

解决方案

条件永远为真，因为没有整数同时等于 1 和 2 (selection != 1) || (selection != 2) || (selection != 3) || (selection != 4) || (selection != 5)。char selection;

您应该使用&&（逻辑与）而不是||（逻辑或）。

此外，您可能希望将输入与类似的字符'1'进行比较，而不是像1.

总之，条件应该是：

(selection != '1') && (selection != '2') && (selection != '3') && (selection != '4') && (selection != '5')

或者您可能想要更简单的一个：

selection < '1' || '5' < selection

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