Question

How do pointers work with the concepts of Object oriented programming?

As I understand it (and please recognize, I’m classified as an ID-10T), the main tenet of OOP is containment and keeping management responsibility (memory/implementation/etc.) contained within the class; but when an object’s method returns a pointers it seems like we are ‘popping‘ the object. Now, somebody might need to worry about:

1. Are they supposed to delete the pointer’s associated object?
2. But what if the class still needs the object?
3. Can they change the object? If so, how? (I recognize const might solve this issue)
4. and so forth…

It seems the user of the object now needs to know much more about how the class works and what the class expects of the user. It feels like a “cat’s out of the bag” scenario which seems to slap in the face of OOP.

NOTE: I notice this is a language independent question; however, I was prompted to ask the question while working in a C++ environment.

Answer 1

What you describe are ownership issues. These are orthogonal (i.e. independent, you can have either without the other or even both) to object orientation. You have the same issues if you do not use OOP and juggle pointers to POD structs. You don’t have the issue if you use OOP but solve it somehow. You can (try to) solve it using more OOP or in another way.

They are also orthogonal to the use of pointers (unless you nit pick and extend the definition of pointer). For example, the same issues arise if two separate places hold indices into an array and mutate, resize and ultimately delete the array.

In C++, the usual solution is to select the right smart pointer type (e.g. return a shared pointer when you wish to share the object, or a unique pointer to signify exclusive ownership), along with extensive documentation. Actually, the latter is a key ingredient in any language.

One OOP-related thing you can do to help this is encapsulation (of course, you can have encaptulation just fine without OOP). For instance, don’t expose the object at all, only expose methods which query the object under the hood. Or don’t expose raw pointers, only expose smart pointers.