Question

in java we can do this:

public class A{

    public static void main(String...str){
        B b  = new B();
        b.doSomething(this);   //How I do this in c++ ? the this self reference
    }
}


public class B{
    public void doSomething(A a){
        //Importat stuff happen here
     }
}

How can I do the same but in c++, I mean the self reference of A to use the method in B ?

Answer 1

First, in a static method there is no this parameter. Anyway, assuming that main() is not static here is how you can do it in C++

class A {
public:
   void f() { 
      B* b = new B();  
      b->doSomething(this);
   }

   void g() { 
      // ...
   };
};


class B {
public:
   void doSomething(A* a) {
       // You can now access members of a by using the -> operator:
       a->g();
   }
};

In C++ this is a pointer to the “current” Object. Thus if you define doSomething() as taking a pointer to A (that is: doSomething(A* a)), then you will be able to receive the this of A. The -> operator will give you access to the members of the a parameter, as follows: a->g().

Alternatively you can pass *this and define doSomething() to take a reference to A (that is: doSomething(A& a)):

class A {
public:
   void f() { 
      B* b = new B();  
      b->doSomething(*this);
   }

   void g() { 
      // ...
   };
};


class B {
public:
   void doSomething(A& a) {
       // You can now access members of a by using the . operator:
       a.g();
   }
};

To access members of a reference you need to use the . (dot) operator: a.g().