SOLID Design Principles

Hello everyone and welcome back.

 This week I will be exploring three of the five design principles of OOP; Single Responsibility Principle (SRP), Open-Closed Principle (OCP), Liskov’ Substituion Principle (LSP), Interface Segregation Principle (ISP), and Dependency Inversion Principle (DIP).

My first introduction to these principles was in reading “Clean Code: A Handbook of Agile Software Craftsmanship” by Robert C. Martin. Prior to learning these concepts, my code was messy and not easily modified. I used to put way too many methods in classes, and my child classes were not fully compatible with the parent classes. I chose this topic because we all benefit when our code is adaptable, clear-cut and easy to maintain. I chose this blog because the author presents the information in a very direct format with great examples.

The purpose of these design principles is to make our code easier to maintain, change and understand. As software engineers, a lot of the code most of us will be working on will be code that others have written. There will be others who will be maintaining our code when we are no longer working on it. When we follow these design principles, not only do we improve our coding skills, but we help those who maintain the code we have written.

Single Responsibility Principle (SRP) means that a class should have only one purpose/task that it is responsible for. This makes code more maintainable by making software more comprehensible for future changes to be made. If a single class has multiple responsibilities, editing in the future will be more complicated because we will have to make additional changes to the classes that are dependent on it. You will have to update and recompile dependent classes that are not directly related to the change you needed to make.

Open-Closed Principle (OCP) means functions, classes and modules should be written such that others can add to them but not change the core elements. When we use this principle our code, our software will give less errors when requirements change. This makes our code more robust and reusable.

Liskov’s Substitution Principle states that every dependent class should be substitutable for their parent class without breaking functionality. Our validation rules on input parameters in subclasses should not be stricter than the input parameters on the parent. Using this principle increases maintainability of our software by making our class hierarchies easier to understand.

Through utilizing these design principles, I will be a better software engineer. I am more aware of ways to improve the legibility, and modifiability of my code. These design principles will help me stay away from poor coding practice.

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