calling a function in a class's “owner” class

Question

Following pseudocode sums up my question pretty well I think...

class Owner {
    Bar b = new Bar();

    dostuff(){...}
}    

class Bar {
    Bar() {
        //I want to call Owner.dostuff() here
    }
}

Bar b is 'owned' (whats the proper word?) by Owner (it 'has a'). So how would an object of type Bar call Owner.dostuff()?

At first I was thinking super();, but that's for inherited classes. Then I was thinking pass an interface, am I on the right track?

Answer 1

This would work:

class Owner {

    Bar b = new Bar(this);

    dostuff(){...}
}    

class Bar {
    Bar(Owner myOwner) {
        myOwner.dostuff();
    }
}

Answer 2

There are 3 possibilities :

1) making dostuff() static and call it like

Owner.dostuff()

2) Creating an instance of Owner inside the class Bar

class Bar {
   Owner o;
   public Owner() {
     o = new Owner();
     o.dostuff();
   }
}

3) Inject an Owner instance through the constructor

class Bar {
   public Owner(Owner o) {
     o.dostuff();
   }
}

Answer 3

class Owner {
    Bar b = null;
    Owner(){
       b = new Bar(this);
    }
    dostuff(){...}
}    

class Bar {
    Owner o = null;
    Bar(Owner o) {
        this.o = o;
    }
}

Now, instance b of Bar has a reference to o of type Owner and can do o.doStuff() whenever needed.

Answer 4

I think the way you have written the code, it is not possible to do. But if you declare Bar as inner class of Owner, you might get a closer solution.

Answer 5

class Owner {

    Bar b = new Bar(this);

    dostuff(){...}
}    

class Bar {
    Bar(Owner owner) {
       owner.doStuff();
    }
}

Answer 6

In the way you're putting it, there is no way of calling the "owner" in Java.

Object A has a reference of object B doesn't mean that object B even knows that object A exists.

The only way to achieve this would be either though inheritance (like you said yourself), or by passing an instance of object Owner to the constructor of Bar.