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Thu. Sep 21st, 2023

In the present day I want to discuss S.O.L.I.D., the primary 5 ideas of object-oriented programming that we discover important for constructing working software program. In case you did not realize it, in pc programming, the SOLID ideas acronym was launched by Michael Feathers for 5 ideas that had been outlined by Robert C. Martin within the early 2000s.

As , to get a working software program, we must always have a low coupling, excessive cohesion and robust encapsulation, which is one thing that the SOLID ideas assist us acquire. The thought is that, by making use of these ideas collectively, you’ll be able to write higher high quality code that’s sturdy. The system created turns into simple to take care of, to reuse and to increase over time. Mainly, SOLID ideas assist software program builders to attain scalability and keep away from that your code breaks each time you face a change.

OK, so let’s begin with the fundamentals, S.O.L.I.D. stands for:

S – Single-responsibility precept

O – Open-closed precept

L – Liskov substitution precept

I – Interface segregation precept

D – Dependency Inversion Precept

Let’s take a look at every precept individually to know why S.O.L.I.D may help builders to construct high quality software program.

The SOLID Rules

1.Single-responsibility precept

“There ought to be by no means multiple cause for a category to alter.”

As you’ll be able to see, this precept states that an object / class ought to solely have one duty and that it ought to be utterly encapsulated by the category. Right here, once we discuss a duty, we imply a cause to alter. This precept will result in a stronger cohesion within the class and looser coupling between dependency courses, a greater readability and a code with a decrease complexity.

It’s way more obscure and edit a category when it has varied obligations. So if we have now multiple cause to alter, the performance might be cut up into two courses and every will deal with its personal duty.

We care about separating the functionalities as a result of every duty is an entry of change. When a category has greater than a single duty, these obligations grow to be coupled and this coupling can result in a fragile code base that’s tough to refactor when your necessities emerge.

2. Open-closed precept

“Software program entities (courses, modules, features, and many others.) ought to be open for extension, however closed for modification.”

Right here, the concept is that an entity permits its behaviour to be prolonged however by no means by modifying its supply code. Any class (or no matter you write) ought to be written in such a approach that it may be used as is. It may be prolonged if want be, however it may well by no means be modified. You possibly can think about this if you end up writing your courses. Use the category in any approach you want, however modifying its behaviour comes by including new code, by no means by modifying the outdated. The identical precept may be utilized for modules, packages, libraries.

By making use of the open-closed precept you’ll get a unfastened coupling, you’ll enhance readability and eventually, you can be lowering the danger of breaking present performance.

three. Liskov substitution precept

“subtypes should be substitutable for his or her base sorts”

Because it’s title says it, Likov’s Substitution Precept was outlined by Barbara Liskov. The thought right here is that objects ought to be replaceable by situations of their subtypes, and that with out affecting the functioning of your system from a consumer’s standpoint. Mainly, as a substitute of utilizing the precise implementation, you need to at all times have the ability to use a base class and get the outcome you had been ready for. Usually once we wish to characterize an object, we mannequin our courses based mostly on its properties and as a substitute of that, we must always really be placing extra our give attention to the behaviours.

This precept mainly confirms that our abstractions are right and helps us get a code that’s simply reusable and sophistication hierarchies which might be very simply understood.

What many say is that Liskov’s Substitution Precept has a really sturdy relation with the earlier precept, the open-closed precept. Robert C. Martin even says that “a violation of LSP is a latent violation of OCP”.

four. Interface segregation precept

“Courses that implement interfaces, shouldn’t be compelled to implement strategies they don’t use.”

Right here, it is about the best way to write interfaces. So what’s said? Mainly, as soon as an interface is changing into too giant / fats, we completely want to separate it into small interfaces which might be extra particular. And interface might be outlined by the consumer that can use it, which implies that consumer of the interface will solely know concerning the strategies which might be associated to them.

Really, when you add strategies that should not be there, the courses implementing the interface should implement these strategies as nicely. That’s the reason; consumer should not be compelled to rely on interfaces that they do not use. ISP is meant to maintain a system decoupled and thus simpler to refactor, change, and deploy.

5. Dependency Inversion Precept

“Excessive degree modules shouldn’t rely on low degree modules moderately each ought to rely on abstraction. Abstraction shouldn’t rely on particulars; moderately element ought to rely on abstraction.”

Final of the SOLID ideas however not least, this precept is primarily involved with lowering dependencies amongst the code modules. Mainly, the Dependency Inversion Precept might be of an incredible assist on the subject of understanding the best way to accurately tie your system collectively.

In case your implementation element will rely on the higher-level abstractions, it’s going to make it easier to to get a system that’s coupled accurately. Additionally, it’s going to affect the encapsulation and cohesion of that system.


When creating any software program, there are two ideas which might be essential: cohesion (when completely different components of a system will work collectively to get higher outcomes than if every half can be working individually) & coupling (may be seen as a level of dependence of a category, technique or another software program entity).

Coupling is often current in a whole lot of code and as I discussed earlier, the optimum state of affairs can be to have a low coupling and a excessive cohesion. With this transient introduction to the 5 SOLID ideas, it’s essential to have understood that they assist us on the subject of that.

There are such a lot of ideas in software program engineering and I’d suggest that earlier than writing a code, you need to do your analysis, learn and attempt to perceive the ideas. Though it might look like quite a bit, SOLID turns into part of you and your code through the use of it repeatedly and adapting its tips.

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