OOP Principles

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1. Why OOP? What's wrong with procedural code? -- "structured programming" Why Object Oriented Programming?
2. Why OOP? OOP benefits Developers We naturally think/talk in terms of objects, attributes, behaviors, interactions, events - Should present a useful Model of the real world - Expressive: exposes how things work in plain language - Helps reason about your problem domain - Handles increasing complexity Samples: github / Cart
3. What is OOP? Using Classes: Encapsulation, Inheritance, Polymorphism (blah blah…) OOP Principles 1) Single Responsibility 2) Encapsulation 3) Semantic Modeling 4) Loose Coupling 5) Types of Objects
4. OOP Principles 1) Single Responsibility: • Small, single task Classes + Small single-task Methods • A class should have only one reason to change • Separate Queries (->get*) & Commands (->update*) • Use Factory classes ( CartFactory::Create() )
5. OOP Principles 2) Encapsulation: • Expose "Public API" for class, Hide implementation -- default to ‘protected’ not public • Self-validating objects
6. OOP Principles 3) Semantic Modeling: • Semantic Naming (avoid names like "xxxManager") • Model Relationships ("Is-A", "Has-A" etc) Favor composition over inheritance -- unless you are building a framework
7. OOP Principles 4) Loose Coupling: • Modules -- high cohesion, internal dependencies • Use interfaces // Type Hinting • Dependency Inversion: Constructor/Setter injection • Use Events // Commands // Services
8. OOP Principles 5) Types of Objects: • Entities -- have an identity and a lifecycle • Value Objects -- descriptive, immutable data objects • Aggregates -- Composite Objects w/Root Entity • Collections & Repositories