Object-Oriented Programming Synonyms

This post is written for my classmates at DigiPen.

Most of the class have started learning object-oriented programming really for only two weeks, and the professor uses quite a few synonyms that sound really different but are actually the same things. I thought it is very confusing to many new-comers to OOP, so I felt like writing a post to clarify things up. I’ll just group synonyms of the exact same meaning together:

When class B inherits from class A, we can also say:
Class B is derived from class A.
Class B extends class A.

If class B inherits from class A, we say:
Class B is the subclass, and class A is the superclass.
Class B is the child class, and class A is the parent class.
Class B is the derived class, and class A is the base class.

When we declare a variable C in class A, we say:
C is a data member of A.
C is a field of A.
C is a property of A.
(As Ryan pointed out in the comment, properties in many object-oriented languages may involve implicit getters and setters)

When we declare a function D in class A, we say:
D is a member function of A.
D is a method of A.

This is pretty much what we need to know right now. I hope this post clarifies things up a little bit.

About Allen Chou

Physics / Graphics / Procedural Animation / Visuals
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7 Responses to Object-Oriented Programming Synonyms

  1. caroparo says:

    A more abstract relationship between parent & children:
    – if class B inherits from class A, B “is-a” A

    Between data members and owner class:
    – if a variable of class C is declared in class A, A “has-a” data member C

  2. Nate nate nate nate nate nate nate nate says:

    Children derive from their parents? I thought they were just farther down a tree.

  3. Ryan says:

    Looks good mostly.
    I wouldn’t call member variables properties in c++ though. In most object oriented languages, properties have implicit setters and getters that can be full functions. Plus some implementations of c++ (I’m looking at you Microsoft) have real properties through crazy compiler intrinsics(not standard in any way).

    • CJ Cat (Allen Chou) says:

      Yeah, the properties in C# could be implicit getters and setters. Maybe the more proper name for data members is field? I just took it from Java and ActionScript, where data members are called properties (ActionScript also has implicit getter/setter feature). Thanks for pointing it out.

      • caroparo says:

        I like the term “property”, in that we can say “children inherits properties from their parent”. Properties in C# do mean different things than fields; as mentioned above they are automatically generated or explicitly implemented (saves the naming nonsense) getters and setters, similar to @synthesized / @property in objective C.

  4. Nawid says:

    Thanks a lot for these clarifications!
    I also really like how you formatted this 😀

    • CJ Cat (Allen Chou) says:

      Glad you like it 🙂

      I actually borrow this format from my Linear Algebra textbook, where it always groups more than 5 (sometimes even more than 10) mathematically equivalent statements together to make sure you understand every aspect of a fact. It seemed crazy at first, but later on I really appreciate such formatting, for it covers a topic very thoroughly and effectively.

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