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

One way of finding out when you need to create an object and when not is to write down a short description of what you are trying to accomplish in plain language. If you are happy that you managed to express the problem in your description you can then pick the objects from that text as candidate classes. Then remove those that are obviously not needed.

Of course you will usually add many more classes to your SW and you will still remove some that you chose this way, but this is a starting point that I have used often. I usually end up drawing a crude ER diagram after this which further clarifies which classes I need. I also look at the candidate classes for similarities for inheritance purposes.

So if you feel the need to explain the keyhole in your short description then it's a good candidate for a class. If not, it might later still become apparent that you need a separate class for it but at that point you should already have a good idea of what you are doing in any case.