成员函数在主函数中可访问，但在 while 循环中抛出错误"not declared in this scope"

Question

我正在尝试制作一个简单的循环菜单。我将成员函数 mainMenu() 移到了 main() class 上面，正如互联网上建议的那样

但是当我尝试从 while 循环中调用 mainMenu() 时，编译器给出了以下错误，如注释中所述：

'mainMenu' was not declared in this scope

下面是头文件。我一直在搞乱类型，试图让错误消失，我不知道这是否能解决任何问题。如果mainMenu()不是成员函数，那么什么是成员函数？

Main.h

class main
{
    private:
    //variables
    bool quit;
    int userSelect;

    //constructor
    main();

    //methods
    mainMenu();
};

main.cpp

#include <iostream>

#include "Main.h"
using namespace std;

int main() {

bool quit = false;
int userSelect;

//mainMenu(); //** placing it here does not cause any errors **
while(!quit) {
    //Main Screen
    mainMenu(); // **actually I want it here, but I get the above error **
    cin >> userSelect;

    cin.ignore();
    switch (userSelect) {
        case '1':
            //moveInventory
            break;
        case '2':
            //viewInventory
            break;
        case '3': //user wants to exit
            //exit
            break;
        default:
            cout << "Command not recognized";
            mainMenu();
            break;
        }
    }

    return 0;
} //end of main

void mainMenu() {
    cout << "Welcome to the Simple Distribution Center.\n"
            "1) Move Inventory\n"
            "2) View Inventory\n"
            "3) Save and Exit" << endl;
}

Answer 1

不要使用 main 作为 class 名称，创建您想要的成员函数 public 并使用完整签名

userIO.h:

class userIO        // using `userIO` so its not confusing
{
private:
  // variables -- NONE

public:             // you need member functions public so they can be called
  enum choice { moveInventory=1, viewInventory=2, QUIT=3 }; // QUIT must be last

// constructor Not Needed

// static methods, since class has no data
  static void mainMenu();   // you need a full signature, *void*
  static choice userChoice();
};

并且您必须使用 :: 告诉编译器您的代码属于您的 class 请注意，所有 iostream 都包含在这里，最好将 using namespace std; 也隔离在这里

userIO.cpp:

#include <iostream>
#include "userIO.h"

using namespace std;

void userIO::mainMenu() {
    cout << "Welcome to the Simple Distribution Center.\n"
            "1) Move Inventory\n"
            "2) View Inventory\n"
            "3) Save and Exit" << endl;
}

userIO::choice userIO::userChoice() {
  int userSelect;

  while(1) {
    cin >> userSelect;
    cin.ignore();

    if ((userSelect < moveInventory) || (userSelect > QUIT)) {
      cout << "Command not recognized" << endl;
      mainMenu();  // Note no need for userIO:: since it's the same class
    } else {
      return choice(userSelect) ;
    }
  }
}

main.cpp:

#include "userIO.h"

int main() {
  bool quit = false;

  while(!quit) {
    userIO::mainMenu(); 
    switch (userIO::userChoice()) {
        case userIO::moveInventory :
            // code to move inventory here
            break;
        case userIO::viewInventory :
            // code to view inventory here
            break;
        case userIO::QUIT :
            quit=true;
            break;
        // NOTE: no default needed since only valid choices are returned
        }
    }

    return 0;
}

成员函数在主函数中可访问，但在 while 循环中抛出错误"not declared in this scope"

Member function accessible in main function, but in while loop throws error "not declared in this scope"

c++

menu

member-functions

while-loop

Main.h

main.cpp