A Beginner’s Guide to Object-Oriented Programming with Apex: 0. An Introduction
Over the next few weeks and months I will be releasing articles that describe and show the basics of object-oriented programming (OOP) with Apex. My approach will be to make these articles as modular and simple as possible. The target audience? Developers with a-teeny-bit-of-experience through to those who have tons of experience but never had any formal training in OOP.
What the hell is OOP?
Good question, and although many agree on some elements of OOP there is still a divergent view in the details. Contrasting it to what came before helps though.
The programming paradigm prior to OOP essentially had everyone writing code as your would an essay i.e. a single long text with one line written (and executed) after the other. There were no classes, no methods, no GOTO statements even (if you go far back enough that is). If you needed the same complex calculation in 5 parts of your application you had to write it 5 times. This is obviously a bad idea and over time the geniuses that created computer programming started inventing bits and pieces of engineering to make it easier to create, maintain and extend their code. Collectively, these features together with their experience were the beginnings of OOP.
The most commonly cited features of OOP are described below.
A way to hide state (or private data), but also – confusingly – a way to bundle data and capabilities to operate on that data.
As an example consider a sausage making machine, you pour some stuff into one end and get sausages out of the other without needing to know the internal workings. The inner workings are encapsulated within the machine.
This is one of the trickiest concepts because it is relative, you can have levels of abstraction and it essentially means providing the appropriate level of information and data at the requested level.
With my previous example, if you are the sausage maker then you just need to know what stuff to insert into which part of the machine. But, if you were the sausage machine repair man you would need to have the tools, knowledge and access to all the bits and bobs inside of the machine. These are different levels of abstraction.
A controversial aspect since some languages think that inheritance is bad. In short it is the capability of a class or object to have certain methods and attributes passed down to them through a hierarchy.
Now that I’ve started the sausage story I can’t stop! All sausages share certain qualities e.g. they’re all encased in something, have some type of contents and (usually) need to be cooked before being eaten. You could represent these common attributes in a parent class and have specific types of sausages (pork, chicken, blood pudding) “subclass this superclass” i.e. inherit from it.
Polymorphism is extremely rewarding when you get it right because it just feels smart. In short it allows you to define ways of dealing with data without knowing exactly how that data will be defined in the future.
To finish off the sausage story (anyone else hungry?) you could put any type of meat into the machine but in the end you will still always get a sausage i.e. provided that a certain type of input (any type of meat and spice) is provided to the machine it “knows” what to do with it (make delicious sausages) even though the types of sausages may have differences.
Don’t worry if these concepts haven’t clicked just yet, each will be covered in detail in future posts.
These concepts are obviously academic and language agnostic but Apex makes them available to you through the constructs of classes, methods and attributes of those classes, instances of those classes.
A note on terminology. In the Salesforce world an Object is most commonly used to refer to a data entity e.g. Account or CustomObject__c. In the OOP paradigm an Object is an instance of a Class i.e. MyClass.cls is an Apex class which provides the blueprint for instances of itself. This becomes clearer with an example:
MyClass myObject = new MyClass(); myObject.divideByZero();
MyClass is the class, and myObject is an instance of that class AKA an object. Got it? Great.
Why Should I Use OOP?
Because it will make you a better programmer and it doesn’t hurt with the ladies/men (delete as appropriate). Your code will be better, you will end up doing less boring work and it will be easier (and quicker) to fix bugs. I guarantee it.
Next Time on Th3Silverlining
My next post will delve into the feature called Encapsulation so hit the subscribe button to find out when it’s published. See y’all then.