A Brief Introduction to Object-Oriented Programming (OOP)

Why is OOP so powerful and popular?

• Everyone loves it.

• Reusable code.

• Simple to debug.

• Because Comp. Sci. Professors say so.

Answer explanation

Object-oriented programming (OOP) is about modelling a system as a collection of objects, where each object represents an aspect of the system. Objects contain both data and methods/functions. 

• - Good: highly reusable code.

• - Bad: increased complexity.

What is a Class?

• A "recipe" used to create objects

• An object

• Where I take my courses

• An recursive function

Answer explanation

• - Class: The “recipe,” or code, that defines an object. E.g., the “Cookie” definition in code.
  
  - Object/Instance: When we run our code, the class (“recipe”) is used as a template to create an object, using the “new” keyword we can use in our code. We can create multiple objects from one class.

What is abstraction in OOP?

• Hiding all information from others.

• Making things obtuse.

• Hiding the complex implementation details and showing only the necessary features of an object.

• Showing only the complex parts.

Answer explanation

We can control the visibility of internal mechanisms, exposing a much simpler interface to other parts of the program.

E.g., We may call someCookie.addSprinkles() from another area of the program, and yet we don’t need to know how that method/function works.

What is encapsulation in OOP?

• Allowing access to all parts of an object.

• Bundling all complexities and hiding them.

• A method to increase usability.

• Bundling data and methods into a single object.

Answer explanation

Refers to the ability to “bundle” data and properties into an object and control their visibility to other parts of the program.

E.g. a “Cookie” Class has protected properties (numChocolateChips, radius), and we can ”get” all of these through accessors of the cookie object like the public someCookie.getRadius().

What is Inheritance in OOP?

• Process of creating a new class.

• Passes on method parameters to other methods.

• Allows a new class to retain wealth.

• Allows a new class to inherit properties and behaviors from an existing class.

Answer explanation

We can reuse code from other classes by creating a new class that extends another. This allows us to create variations of a class without having to duplicate code.

E.g.,  We can create another class called ”Biscotti” that inherits from “Cookie.” A biscotti is very different from a traditional “cookie” but will share many properties (e.g., numChocolateChips) and methods (bake()). We may also add other properties, like private length and private height.

What is polymorphism in OOP?

• Limits access to methods and data.

• Allows objects of different classes to have different behaviours through similar interfaces.

• Is a way to change things.

• Allows an object to change class.

Answer explanation

Allows different objects to have different functionality when calling the same method.

E.g., we may override the method of “bake()” in the class “Cookie” to bake a biscotti differently in the “Biscotti” class. We can use the same method name (bake()) on objects from both classes, but they work very differently.