OOP: When is it an object?

Question

I\'m trying to understand object orientation. I understand it a little bit of course, but sometimes I\'m not 100% clear. How do you decide what should be turned into an object (

Answer 1

Another way to look at it is whether or not the doorknob is interchangeable. I would make the doorknob a separate object that is a property on the door. One question is whether or not you want to make the doorknob a private class if only the door can have that knob. I personally prefer not use a private class here, but is a legitimate possibility. By using a separate object as a property on the door, you can now move that instance of the knob from one door (instance) to another (like exchanging knobs from one door to another in your house).

Another interesting aspect of this is extending your hierarchy... You might have fancy knobs, lockable knobs, etc, which can all be implemented by extending your base door knob.

I hope that helped a little to clarify your confusion.