C++ - 如何從調用函數的變量，而無需使用全局變量

Question

我一直在試圖完成一項任務，但我不允許使用全局變量。

如果你必須做出一個咖啡店計劃，使用戶可以買咖啡（小型，中型或大型），然後顯示出售咖啡杯的總數，然後再從賣咖啡製作總銷售額的任務。我完成了用戶可以購買的一半代碼，但我堅持總結咖啡銷售/杯子。

功能cupsSold和總金額返回0或垃圾值。我也不允許使用額外的庫函數。

有什麼辦法來從另一個調用函數變量，而無需使用全局變量？

這是我的主要代碼：「有沒有辦法從另一個調用函數變量，而無需使用全局變量」

#include <iostream> 
using namespace std; 

void showChoices() 
{ 
    cout << "Welcome to Jason's Coffee Shop\n\n"; 
    cout << "1. Buy Coffee" << endl; 
    cout << "2. Show total cups sold by size"<< endl; 
    cout << "3. Show total amount of coffee sold"<<endl; 
    cout << "4. Show total amount of money made"<< endl; 
    cout << "0. Exit" << endl; 
    cout << "\nYour choice: "; 
} 

void buyCoffee(int numberSmCups,float totalSmCups,int numberMedCups,float totalMedCups, int numberLgCups,float totalLgCups) 
{ 

    char coffeeSize, order = 'y'; 
    bool coffeeSelect = true; 
    float smCoffee = 1.75, mdCoffee = 1.90, lgCoffee = 2.00, totalCoffee = 0; 

    while(coffeeSelect) 
    {   
     if (order == 'y' ||order =='Y'){ 

     cout << "Size of Coffee [S, M, L]: "; 
     cin >> coffeeSize; 

     if (coffeeSize == 's' || coffeeSize == 'S') 
     { 
      cout << "Quantity of Small Coffee: "; 
      cin >> numberSmCups; 
      totalSmCups = numberSmCups * smCoffee; 
      cout << "Small Coffee: "<<numberSmCups<<", Bill: "<<totalSmCups<<endl; 
      totalCoffee += totalSmCups; 
      cout << "Add another coffee [Y or N]: "<<endl; 
      cin >> order; 
     } 
     else if (coffeeSize == 'm' || coffeeSize == 'M') 
     { 
      cout << "Quantity of Medium Coffee: "; 
      cin >> numberMedCups; 
      totalMedCups = numberMedCups * mdCoffee; 
      cout << "Medium Coffee: "<<numberMedCups<<", Bill: "<<totalMedCups<<endl; 
      totalCoffee += totalMedCups; 
      cout << "Add another coffee [Y or N]: "<<endl; 
      cin >> order; 
     } 
     else if (coffeeSize == 'l' || coffeeSize == 'L') 
     { 
      cout << "Quantity of Large Coffee: "; 
      cin >> numberLgCups; 
      totalLgCups = numberLgCups * lgCoffee; 
      cout << "Large Coffee: "<<numberLgCups<<", Bill: "<<totalLgCups<<endl; 
      totalCoffee += totalLgCups; 
      cout << "Add another coffee [Y or N]: "; 
      cin >> order; 
     } 
     } 
     else 
      break; 
    } 

    cout << "--------------\n"; 
    cout << "Your invoice: "<<endl; 
    cout<< endl; 
    if (numberSmCups>= 1) 
     cout << "Small Coffee: "<< numberSmCups <<" cups ($ "<< smCoffee <<"/cup) Amount: $ "<< totalSmCups << endl; 
    if (numberMedCups>=1) 
     cout << "Medium Coffee: "<< numberMedCups <<" cups ($ "<< mdCoffee << "/cup) Amount: $ "<< totalMedCups << endl; 
    if (numberLgCups>=1) 
     cout << "Large Coffee: " << numberLgCups <<" cups ($ " << lgCoffee << "/cup) Amount: $ " << totalLgCups << endl; 
    cout<< endl; 
    cout << "Total Amount: "<<"$ "<< (totalSmCups+ totalMedCups+ totalLgCups) << endl; 
    cout << "--------------" << endl; 

} 

void cupsSold(int numberSmCups,int numberMedCups,int numberLgCups){ 
    int lifeSmCups=0; 
    int lifeMdCups=0; 
    int lifeLgCups=0; 

    lifeSmCups = lifeSmCups + numberSmCups; 
    lifeMdCups = lifeMdCups + numberMedCups; 
    lifeLgCups = lifeLgCups + numberLgCups; 

    cout << "Total Small cups: "<<lifeSmCups<<endl; 
    cout << "Total Medium Cups:"<<lifeMdCups<<endl; 
    cout << "Total Large Cups:"<<lifeLgCups<<endl; 
} 

void totalAmount(float totalCoffee) 
{ 
    cout << "Total: "<<"$"<<totalCoffee<<endl; 
} 

int main() 
{ 
    int numberSmCups = 0, numberMedCups = 0, numberLgCups = 0, choice; 
    float totalSmCups = 0, totalMedCups = 0, totalLgCups = 0, totalCoffee; 

    while (choice != 0) 
    { 
     showChoices(); 
     cin >> choice; 
     cout << endl; 

     if (choice == 1) 
     { 
      cout <<"You selected to buy coffee."<< endl; 
      buyCoffee(numberSmCups,totalSmCups,numberMedCups,totalMedCups,numberLgCups,totalLgCups); 
     } 
     else if (choice == 2) 
     { 
      cout << "The total amount of cups sold by size is: "<<endl; 
      cupsSold(numberSmCups,numberMedCups,numberLgCups); 
     } 
     else if (choice == 3) 
     { 
      cout << "Total Coffee Sold: "<<endl; 
      // cupsSold(numberSmCups,numberMedCups,numberLgCups); 
     } 
     else if (choice == 4) 
     { 
      cout << "Money made from coffee sales: "<<endl; 
      totalAmount(totalCoffee); 
     } 
     else if (choice == 0) 
     { 
      cout << "EXIT"<<endl; 
      break; 
     } 
     else 
      cout << "Invalid Input" << endl; 
    } 

    return 0; 
} 

Answer 1

您需要通過參考使用參數，如果你想改變傳遞給函數的變量，這樣

void cupsSold(int& numberSmCups,int& numberMedCups,int& numberLgCups){ 
       //^    ^    ^

否則，這些功能只是副本，而不是原來的變量值進行操作。