c++ - How do you approach a private variable from a different class -

void user :: buyapples(){    while(1){         cout<<"how many want buy? press 0 quit.";cin>>qq;          if(qq==0)             return ;          if(qq<= f.getnumofapples()){             if(salary>=(qq*200)){                 invofapples+=qq;                 salary-=(qq*200);                 showsalary();                    }             else{                 cout<<"not enough money"<<endl;                 void homescreen();             }         }         else{             cout<<"there's not enough apples in stock"<<endl;             continue;         }     } } 

this code market qq being input using cin.

i can change salary , private variables in user class.

but need change private variables in fruit class int numofapples. how can change numofapples?

i can't seem change variable user class. when tried change fruit class, qq doesn't carry over. do?

if want access private variable class should implement public method in class, get/set method example.

with preserve visibility of variable