c++ - 如何从另一个函数读取函数中的输入值？

Question

嘿，我是初学者，对 C++ 知之甚少。我试图在函数的帮助下开发一个库存系统，但我似乎无法在另一个函数中使用我在一个函数中输入的输入。

可以做到吗？如果可以，怎么做？代码如下。还没有完成，我只是想展示我创建的所有功能。

这里我想在void displayData()中显示void input()的输入

    #include <iostream>
    #include <string>
    using namespace std;

    void introDisplay (char&n)
    {

    cout << "                                           ______MOON'S 
    INVENTORY SYSTEM_____" << endl;
     cout << "*To insert data press 'i'" << endl;
     cout << "*To delete data press 'd'" << endl;
     cout << "*To edit data press 'e'" << endl;
     cout << "*To update data press 'u'" << endl;
     cout << "*To display data of all fields press 'v'" << endl;
     cout << "*To display all the menu press 'm'" << endl;

     cin >> n;

     }

    void menu ()

    {

     cout << "Data Fields are: " << endl;
     cout << "1. Item id" << endl;
        cout << "2. Item name" << endl;
        cout << "3. Item description " << endl;
        cout << "4. Manufacterer" << endl;
        cout << "5. Selling Price" << endl;
        cout << "6. Cost Price" << endl;
        cout << "7. Units in store" << endl;
        cout << "8. Units sold" << endl;
        cout << "9. Year of date first introduced" << endl;
        cout << "10. Month of date first introduced" << endl;
        cout << "11. Day of date first introduced" << endl;

      }
      void input ()
      {
        double itemid;
        cout << "Enter the item ID:" << endl;
        cin >> itemid;
        while (itemid<0)
          {
            cout << "Invalid Item ID. Please type again." << endl;
            cin >> itemid;
          }
        cout << "Item ID: " << itemid << endl;

        string itemname;
         cout << "Type the name of the Item here :" << endl;
         cin. ignore();
         getline (cin,itemname);
         cout << "Item Name: " << itemname << endl;

        string itemdes;
         cout << "What's the description of the item? " << endl;
         cin. clear();
         getline (cin,itemdes);
         cout << "Item Description: " << itemdes << endl;

        string cat;
         cout << "What's the category of the product?" << endl;
         cin. clear();
         getline (cin,cat);
         cout << "Category: " << cat << endl;

      string manufacturer;
       cout << "Who is the manufacturer?" << endl;
       cin. clear();
       getline (cin, manufacturer);
       cout << "Manufacturer: "<< manufacturer << endl;

       double sp;
        cout << "Input the selling price of the item: " << endl;
        cin >> sp;
        while (sp<0)
         {
           cout << "Invalid Number. Please type again." << endl;
           cin >> sp;
         }
        cout << "Selling Price: " << sp << endl;

      double cp;
     cout << "Input the cost price of the item: " << endl;
        cin >> cp;
        while (cp<0)
         {
           cout << "Invalid Number. Please type again." << endl;
           cin >> cp;
         }
        cout << "Cost Price: " << cp << endl;

      double units;
       cout << "Input the number of units left in store: " << endl;
       cin >> units;
       while (units<0)
        {
          cout << "Invalid Number. Please type again." << endl;
          cin >> units;
        }
       cout << "Units in store: " << units << endl;

      double unitssold;
       cout << "Input the number of units sold: " << endl;
       cin >> unitssold;
       while (units<0)
        {
          cout << "Invalid Number. Please type again." << endl;
          cin >> unitssold;
        }
       cout << "Units Sold: " << unitssold << endl;

      int year;
       cout << "Input the year of date first introduced: " << endl;
       cin >> year;
       while (year<0)
        {
         cout << "Invalid Number. Please type again." << endl;
         cin >> year;
        }
       cout << "Year of date first introduced: " << year << endl;

      int month;
       cout << "Input the month of date first introduced: " << endl;
       cin >> month;
       while (month<0 || month>12)
        {
          cout << "Invalid Number. PLease type again" << endl;
          cin >> month;
        }
       cout << "Month of date first introduced: " << month << endl;

      int day;
       cout << "Input the day of the date first introduced: " << endl;
       cin >> day;
       while (day<0 || day>31)
        {
          cout << "Invalid Number. Please type again." << endl;
          cin >> day;
        }
      cout << "Day of date first introduced: " << day << endl;


      }
      void displayData()
      {
        cout << "Item ID: " << itemid << endl;
        cout << "Item Name: " << itemname << endl;
        cout << "Item Description: " << itemdes << endl;
        cout << "Item Category: " << cat << endl;
        cout << "Item Manufacturer: " << manufacturer << endl;
        cout << "Selling Price: " << sp << endl;
        cout << "Cost Price: " << cp << endl;
        cout << "Units in Store: " << units << endl;
        cout << "Units Sold: " << unitssold << endl;
        cout << "Year of date first introduced: " << endl;
        cout << "Month of date first introduced: " << endl;
        cout << "Day of date first introduced: " << endl;

      }

     int main()
     {
       char n;
       introDisplay(n);

       switch (n)
       {
         case 'i':
         input();
         break;

         case 'm':
         menu();
         break;

         case 'v':
         displayData();

         default :
         cout << "Please enter a valid character to continue. Note that the                                                                                  
         characters are case sensitive." << endl;
       }
       system("pause");
       introDisplay(n);
       return 0;
       }

Answer 1

Function 中声明变量的范围仅限于该函数。因此，要么全局声明它们，要么使用 class包含函数和所有变量，类中的函数可以访问变量，但其他函数不能。

class class_name{

    int year,month,day;
    double itemid,sp,cp,units,unitssold;
    string itemname,itemdes,cat,manufacturer;

  public:

    void input();
    void displayData();

  } object_name;

void class_name::input (){ //input method here }
void class_name::displayData(){//displayData method here}

在 main() 中你必须这样调用函数

     object_names.input();
     object_names.displayData();