Question

Observer *o = New Observer();
Subject *s = new Subject() ;
s->register(o);

//Is it a good practice to delete the observer in the unregister function?
//I feel it is not. As the Observer object might still be in use,  for example , 
//it might be registered to another Subject. 
s->unregister(o);  

//So it is safe to rely on the client code to delete the object or rely on the smart pointer things
delete o;

I want to confirm whether my above understanding is correct regarding who should delete the observer object.

Answer 1

I agree with your observation. It is not a good practice to delete the observer in the unregister function – for the simple fact that “one who creates the resource must be responsible for deleting the resource”

This will avoid

• Magic behavior as perceived by the creator.
• Code behavior will be well defined – one who creates must delete. Which will lay overall foundation of understanding of development for new developers to your system.

Similar topic are discussed under lengths in all books with different nomenclature.