c++ - 在另一个成员函数中调用成员函数时，在“int”之前的预期主表达式

Question

我刚刚开始学习 c++，并认为我会尝试通过做一个小项目来衡量我的理解，我正在使用类和成员函数创建一个模拟自动售货机的程序。我只收到以下 2 个错误：“int”之前的预期主要期望

我尝试删除 int，但它给了我对变量错误的未定义引用。任何帮助是极大的赞赏！

#include <iostream>

class DrinkMachine
{
  private:
    const int COST_OF_DRINK = 150;

  public:
    int RunningTotal;

    DrinkMachine()
    {
      RunningTotal = 0;
    }

    void DepositCoins(int money)
    {

      std::cout << "You can deposit coins of values 25, 50 and 100" << std::endl;
      std::cout << "Enter a coin: " << std::endl;

      switch(money)
      {
        case(25):
          RunningTotal += 25;
          break;

        case(50):
            RunningTotal += 50;
            break;

        case(100):
            RunningTotal += 100;
            break;

        default:
            std::cout << "You entered the wrong coin" << std::endl;
            std::cout << "Coins of values 25, 50, 100 are allowed" << std::endl;
            break;
      }
    }


    bool CheckTotal()
    {
      if(RunningTotal >= COST_OF_DRINK)
        return true;

      else
        return false;
    }

    void MakeDrinkSelection(int DrinkChoice)
    {

      bool IsChoiceValid = false;

      while(!IsChoiceValid)
      {
        switch(DrinkChoice)
        {
          case (1):
            std::cout << "Thank you for choosing Coffee!" << std::endl;
            ReturnChange();
            IsChoiceValid = true;
            break;

          case(2):
            std::cout << "Thank you for choosing Hot Chocolate!" << std::endl;
            IsChoiceValid = true;
            ReturnChange();
            break;

          case(3):
            std::cout << "Thank you for choosing Green Tea!" << std::endl;
            IsChoiceValid = true;
            ReturnChange();
            break;

          default:
            std::cout << "Invalid selection. Please re-enter your choice" << std::endl;
            bool NewDrinkChoice;
            DrinkChoice = NewDrinkChoice;
            IsChoiceValid = false;
            break;
        }
      }
    }


    void DisplayDrinks()
    {
      std::cout << "----------------" << std::endl;
      std::cout << "1. Coffee" << std::endl;
      std::cout << "2. Hot Chocolate" << std::endl;
      std::cout << "3. Green Tea" << std::endl;
      std::cout << "----------------" << std::endl;
      std::cout << std::endl;
      std::cout << "Please make a choice: " << std::endl;
      MakeDrinkSelection(int DrinkChoice);  //gives an error

    }

    void ReturnChange()
    {
      if(RunningTotal > COST_OF_DRINK)
      {
        std::cout << "Your change is: " << (RunningTotal - COST_OF_DRINK) << std::endl;
      }
    }
};


int main()
{


  //DrinkMachine drinkmachine = new DrinkMachine();
  DrinkMachine mydrink;

  while(!mydrink.CheckTotal())
  {
    mydrink.DepositCoins(int money); //gives an error
  }

  mydrink.DisplayDrinks();

  return 0;
}

标签： c++functionclass

Answer 1

好吧，代码中有很多错误。我之前没有完全看到他们的程序。我认为你可能做对了。那好吧。

首先，您应该在程序开始时询问机器可以接受哪些硬币，而您没有。

其次，在按值调用函数之前，您应该从用户那里获取输入，然后将其传递给函数，而您又没有这样做。

在这里，我稍微更正了您的代码。

    #include <iostream>

    class DrinkMachine
    {
     private:
        const int COST_OF_DRINK = 150;

      public:
        int RunningTotal;

DrinkMachine()
{
  RunningTotal = 0;
}

void DepositCoins(int money)
{



  switch(money)
  {
    case(25):
      RunningTotal += 25;
      break;

    case(50):
        RunningTotal += 50;
        break;

    case(100):
        RunningTotal += 100;
        break;

    default:
        std::cout << "You entered the wrong coin" << std::endl;
        std::cout << "Coins of values 25, 50, 100 are allowed" << std::endl;
        break;
  }
}


bool CheckTotal()
{
  std::cout << "You can deposit coins of values 25, 50 and 100" << std::endl;
  std::cout << "Enter a coin: " << std::endl;
  if(RunningTotal >= COST_OF_DRINK)
    return true;

  else
    return false;
}

void MakeDrinkSelection(int DrinkChoice)
{

  bool IsChoiceValid = false;

  while(!IsChoiceValid)
  {
    switch(DrinkChoice)
    {
      case (1):
        std::cout << "Thank you for choosing Coffee!" << std::endl;
        ReturnChange();
        IsChoiceValid = true;
        break;

      case(2):
        std::cout << "Thank you for choosing Hot Chocolate!" << std::endl;
        IsChoiceValid = true;
        ReturnChange();
        break;

      case(3):
        std::cout << "Thank you for choosing Green Tea!" << std::endl;
        IsChoiceValid = true;
        ReturnChange();
        break;

      default:
        std::cout << "Invalid selection. Please re-enter your choice" << std::endl;
        bool NewDrinkChoice;
        DrinkChoice = NewDrinkChoice;
        IsChoiceValid = false;
        break;
    }
  }
}


void DisplayDrinks()
{
  int DrinkChoice;                //here declared
  std::cout << "----------------" << std::endl;
  std::cout << "1. Coffee" << std::endl;
  std::cout << "2. Hot Chocolate" << std::endl;
  std::cout << "3. Green Tea" << std::endl;
  std::cout << "----------------" << std::endl;
  std::cout << std::endl;
  std::cout << "Please make a choice: " << std::endl;
  std::cin>>DrinkChoice;              //input by user
  MakeDrinkSelection(DrinkChoice);  //used to give an error

}

void ReturnChange()
{
  if(RunningTotal > COST_OF_DRINK)
  {
    std::cout << "Your change is: " << (RunningTotal - COST_OF_DRINK) << std::endl;
  }
}
};


    int main()
    {


  //DrinkMachine drinkmachine = new DrinkMachine();
  DrinkMachine mydrink;
  int money;              //here declared

  while(!mydrink.CheckTotal())
  {
  std::cin>>money;          //input by user

    mydrink.DepositCoins(money); //no error
  }

       mydrink.DisplayDrinks();

       return 0;
    }

我已经清除了您询问的基本错误。但是你应该自己纠正逻辑上的错误。

希望你会。