SOLID Principles: Introducing Software Architecture & Design

Module 1: Introduction to SOLID Principles

⏳ ~30 min

• Topics: Importance of software architecture; benefits of clean code; evolution from procedural to object-oriented design.

• Hands-on: Watch 5 intro videos and analyze a poorly designed system to set context.

Module 2: Single Responsibility Principle (SRP)

⏳ ~1 hour

• Topics: The idea of one class, one job; breaking up responsibilities; real-world code smells.

• Hands-on: Refactor a monolithic class into multiple cohesive units using SRP.

Module 3: Open/Closed Principle (OCP)

⏳ ~1 hour

• Topics: Extend functionality without modifying existing code; abstract classes and interfaces; plug-and-play design.

• Hands-on: Implement open/closed architecture in a payment gateway use case.

Module 4: Liskov Substitution Principle (LSP)

⏳ ~45 min

• Topics: Ensuring subclasses substitute their parents safely; behavior contracts; avoiding inheritance misuse.

• Hands-on: Break and then fix a class hierarchy to follow LSP in a vehicle example.

Module 5: Interface Segregation Principle (ISP)

⏳ ~40 min

• Topics: Prefer many small interfaces; avoid “fat” contracts; flexible service interfaces.

• Hands-on: Design cleaner APIs for client classes using ISP.

Module 6: Dependency Inversion Principle (DIP)

⏳ ~1 hour

• Topics: High-level modules should not depend on low-level ones; invert control using abstractions.

• Hands-on: Introduce dependency injection and apply DIP in a notification system.

Module 7: Final Architecture & Case Study

⏳ ~1 hour

• Topics: Review SOLID principles; apply all five in a single end-to-end system; software engineering best practices.

• Hands-on: Build a mini project that demonstrates all SOLID principles working together.

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