尝试使用 "while (COM != "Y" || "N" )" 完成由用户输入确定的循环

Question

所以我遇到的问题是在我的 Class IOutro 中，在它的函数 commandInput() 中，我的目的是创建一个简单的基于命令的循环，询问用户是否想再次使用该程序或关闭它。

我对这个程序的目标是类仅用于存储函数，我在 main 中唯一想要的是调用这些函数的对象。第一次尝试 OOP。

因此，当我尝试运行时出现错误。

 ||=== Build: Debug in Tutorials (compiler: GNU GCC Compiler) ===|
C:\Users\Jason\Documents\Tutorials\main.cpp||In function 'int main()':|
C:\Users\Jason\Documents\Tutorials\main.cpp|57|error: could not convert 'COM.std::basic_string<_CharT, _Traits, _Alloc>::operator=<char, std::char_traits<char>, std::allocator<char> >(((const char*)"Y"))' from 'std::basic_string<char>' to 'bool'|
||=== Build failed: 1 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===|

我不确定我应该看什么，我知道这是我使用的字符串的问题，它也给了我一次错误，然后一些更改说它无法识别 !=运算符，我在想 != 意味着 "Is Not Equal To" 而 || 意味着 "Or" （（基本上，如果左边不是真的，检查右边的值，如果左边的值是true，忽略正确的值。))

我确定我遗漏了一些简单的东西，或者我没有查找正确的信息。有哪位大神能赐教吗

这不是作业，我不是学生，我是自学 C++，像这样的地方基本上是我唯一能找到答案的地方。

#include <iostream> // This is a PreProcessor Directive
#include <string> // Do I need this?

using namespace std; // This includes a library???

int A; // Global A
int B; // Global B
string COM = "Y"; // Global used to check if they want to keep going, not sure how to make this not global.

class Arith{ // Class for the calculator stuff.
    public: // Class is public.
        int sum(int A, int B){ // Sum, the actually calculation.
            int C = A + B; // Just math.
            return C; // Return value of C.
        }
        void calc(){ // Calc, not a calculation.
            cout << "Enter a number for A: "; // Ask for A.
            cin >> A; // Get A.
            cout << endl; // Make it look neat.
            cout << "Enter a number for B: "; // Ask for B.
            cin >> B; // Get B.
            cout << endl; // Make it look neat.
            cout << "The sum is: " << sum(A, B); // Print out the sum.
        }
};

class IOutro{ // Class for all informative prompts.
    public:
        void goodbye(){ // The goodbye class
            cout << "Thank you!" << endl; // Display a goodbye.
        }

        void welcome(){ // The welcome class.
            cout << "Welcome!" << endl; // Display a welcome.
        }

        void commandInput(){ // The FML check if they want to keep adding numbers loop of doom...
            cout << "Would you like to continue?" << endl; // Goal is to check if they want to keep going, Y or N.
            cout << "Please type 'Y' for Yes, and 'N' for No." << endl; // They are given options
            cin >> COM; // ???? Get COM

            while (COM != "Y" || "N" ){ // Trying to make it assure they type Y or N, and if they don't it keeps asking.
                cout << "Would you like to continue?" << endl; // Copied the text.
                cout << "Please type 'Y' for Yes, and 'N' for No." << endl; // For this loop.
                cin >> COM; // ???? Get COM, I am pretty sure it's suppose to be getline, but that doesn't work...
            }


        }
};

int main(){ // Indicates a Main Function which returns an Integer?

    IOutro IObject; // Declare the IOutro IObject Object?
    Arith ArithObject; // Same with Arith?

    while (COM = "Y"){ // If they chose Y, run loop
        IObject.welcome(); // Run IObject welcome
        ArithObject.calc(); // Run ArithObject calc
        ArithObject.sum(A,B); // Run ArithObject sum
        IObject.commandInput(); // Run IObject commandInput
    }
    IObject.goodbye(); // If COM != "Y" run IObject goodbye
    return 0; // Return the value 0 to main?
}

Answer 1

让我们看看您的代码中的问题。

首先，你不需要COM是一个字符串，将它声明为一个字符就足够了，比如

char COM = 'Y';

接下来，您应该将 commandInput() 中的 while 循环条件从

更改为

while (COM != "Y" || "N" )

至

while (COM != 'Y' && COM != 'N' )  // if you don't want it to be case sensitive, then you will have to add small letters to the condition as well

你的条件不对，你需要像上面给出的那样检查。

现在您可能想知道为什么我将 || 更改为 &&。这是因为如果它是 ||，如果 COM 不是 'Y' 或者 COM 不是 'N'，循环将继续。现在就这样想，如果COM是'Y'，那么就不是'N'，如果不是'N'，那么你的while循环中的条件就满足了，因此，它只是继续。

现在，让我们看下一个问题。在你的main()中，你有

while (COM = "Y")

其中=是赋值运算符，如果要检查是否相等，则需要使用==。即

while (COM == 'Y' )

所以简而言之，你的代码的固定版本是（我已经删除了你的评论并在我进行了更改的地方添加了评论，有三行更改）

#include <iostream>    
using namespace std;

int A; 
int B;
char COM = 'Y';                    //  changed to char

class Arith{ 
    public: 
        int sum(int A, int B){ 
            int C = A + B; 
            return C; 
        }
        void calc(){ 
            cout << "Enter a number for A: "; 
            cin >> A; 
            cout << endl; 
            cout << "Enter a number for B: "; 
            cin >> B; 
            cout << endl; 
            cout << "The sum is: " << sum(A, B)<<endl; 
        }
};

class IOutro{ 
    public:
        void goodbye(){ 
            cout << "Thank you!" << endl; 
        }

        void welcome(){ 
            cout << "Welcome!" << endl; 
        }

        void commandInput(){ 
            cout << "\nWould you like to continue?" << endl; 
            cout << "Please type 'Y' for Yes, and 'N' for No." << endl;
            cin >> COM;

            while ( ( COM != 'Y' && COM != 'y' ) && ( COM != 'N' && COM != 'n' ) ) {     // made changes here
                cout << "\nWould you like to continue?" << endl; 
                cout << "Please type 'Y' for Yes, and 'N' for No." << endl; 
                cin >> COM; 
            }


        }
};

int main(){ 

    IOutro IObject; 
    Arith ArithObject; 

    while (COM == 'Y' || COM == 'y' ){         // made changes here 
        IObject.welcome(); 
        ArithObject.calc(); 
        ArithObject.sum(A,B); 
        IObject.commandInput(); 
    }
    IObject.goodbye(); 
    return 0; 
}

请注意，对于此代码，您不需要 #include<string> 并且还使代码不区分大小写（即 'Y' 或 'y' 和 'N'或 'n' )

这将消除您遇到的令人讨厌的错误。

好吧，希望能解决问题（好吧，这对我来说已经解决了）

尝试使用 "while (COM != "Y" || "N" )" 完成由用户输入确定的循环

Trying to acomplish a Loop determined by user input using "while (COM != "Y" || "N" )"

c++

oop

boolean

char

while-loop