Course Overview

Welcome to the SOLID Software Design Principles course! This course is designed for software developers, engineers, and anyone interested in building robust, maintainable, and flexible software systems using proven design principles. Whether you’re a beginner looking to understand fundamental design concepts or an experienced developer wanting to refine your skills, this course will help you apply the SOLID principles effectively.

Target Audience

• Beginner Developers: Learn the basics of object-oriented design and get started with best practices in software development.
• Intermediate Developers: Enhance your skills by applying SOLID principles to create more maintainable and flexible codebases.
• Experienced Developers and Architects: Refine your understanding of design principles and explore advanced techniques to improve code quality.

What You Will Cover

Throughout this course, you will explore each of the five SOLID principles in detail:

1. Single Responsibility Principle (SRP): Understanding how to ensure that each class has only one responsibility and how this helps in keeping the code maintainable.

2. Open/Closed Principle (OCP): Learning to design classes that are open for extension but closed for modification, allowing for easier addition of new features.

3. Liskov Substitution Principle (LSP): Exploring how to design class hierarchies where derived classes can be used interchangeably with their base classes without breaking the system.

4. Interface Segregation Principle (ISP): Understanding how to keep interfaces small and focused, avoiding the problem of "fat interfaces" that force classes to implement unnecessary methods.

5. Dependency Inversion Principle (DIP): Learning to decouple high-level modules from low-level details by introducing abstractions, making the system flexible and easy to maintain.

Course Structure

• A broken example first: Each principle starts from code that violates it. The lesson explains exactly what breaks and why, then refactors it.
• Five languages: Every code example is given in Java, Python, C++, C# and JavaScript. Most of them run in the browser, so you can change one and watch the output change with it.
• Problem identification: You will learn to spot the signals of each violation in code you have never seen before, which is what a code review and a design interview both ask for.
• Review at the end of each principle: Every principle chapter closes with a summary, a flashcard deck and a twenty five question assessment.
• A closing chapter: The final chapter takes one class through all five principles in order, then covers the design interview itself.

The course also tells you where each principle stops being worth applying. Applied without judgement these principles produce a maze of interfaces with one implementation each, so every recommendation here comes with its cost.

By the end you will be able to look at unfamiliar code, name what will make it painful to change, propose a fix, and say honestly what that fix costs.