Question

I’m trying to access members of a classC from classB, both classC and classB are inside classA. Here is what I’m trying to do;

            //hello.h
            class hello{
                public:
                   hello();
                   class letters{
                      public:
                         letters();
                         void setName(char n);
                         char getName();
                      private:
                         char name;
                   }
                   class sayHi{
                       public:
                          sayHi();
                          void onJoin();
                   }
            }

            //hello.cpp

            hello::hello(){}
            hello::letters(){}
            hello::sayHi(){}

            void hello::letters::setName(char n){
             hello::letters::name = n;   //trying to access the private variable 'name' inside class letters
            }

            char hello::letters::getName(){
             return hello::letters::name = n; 
            }

            void hello::sayHi::onJoin(){
             cout<< hello::letters::getName() <<endl;
            }

I know i’m doing it wrong, am I supposed to create instances of each class and call the members?

Answer 1

Yes, you’re supposed to create instances of the classes.
These are frequently called “objects”, which is why they call it “object-oriented programming”.

First, your getName and setName should look like this:

void hello::letters::setName(char n) {
    name = n;
}

char hello::letters::getName() const { // Declaration should also say "const".
    return name; 
}

With that out of the way, any sayHi instance needs to know which letters to say “Hi” to, which means that you need to tell it.
This is usually done by passing a parameter to the method that needs to know:

class sayHi{
public:
    sayHi();
    void onJoin(const letters& who)
    {
        cout << who.getName() << endl;
    }
};

which you would use somewhat like this:

int main()
{
    hello::letters letter;
    letter.setName('p');
    hello::sayHi greeter;
    greeter.onJoin(letter);
}