OOP & Design Patterns: Complete Roadmap

Introduction

Object-Oriented Programming (OOP) and Design Patterns are fundamental concepts that every software developer should master. Whether you're building web applications, enterprise systems, or mobile apps, understanding how to structure code using OOP principles and proven design patterns will make you a significantly better developer.

This comprehensive roadmap will guide you through 15 detailed posts covering everything from basic OOP concepts to advanced design patterns.

Why Learn OOP and Design Patterns?

Object-Oriented Programming:

• ✅ Write maintainable, scalable code
  
• ✅ Model real-world problems naturally
  
• ✅ Reuse code effectively through inheritance and composition
  
• ✅ Understand frameworks like Spring Boot, Django, .NET
  
• ✅ Pass technical interviews with confidence
  

Design Patterns:

• ✅ Solve common problems with proven solutions
  
• ✅ Communicate design ideas clearly with team
  
• ✅ Recognize patterns in existing codebases
  
• ✅ Avoid reinventing the wheel
  
• ✅ Build flexible, extensible architectures
  

Who Is This Series For?

• Junior Developers: Moving beyond basic programming
• Self-taught Programmers: Filling theoretical knowledge gaps
• Procedural Programmers: Transitioning to OOP thinking
• Interview Candidates: Preparing for system design questions
• Mid-level Developers: Deepening design pattern expertise

Roadmap Overview

This series is organized into 5 phases with 15 comprehensive posts:

Phase 1: OOP Fundamentals (5 posts)
  └─ Learn the four pillars and core concepts
 
Phase 2: SOLID Principles (1 post)
  └─ Master the five principles of clean OOP design
 
Phase 3: Creational Patterns (4 posts)
  └─ Control object creation effectively
 
Phase 4: Structural Patterns (2 posts)
  └─ Organize classes and objects efficiently
 
Phase 5: Behavioral Patterns (2 posts)
  └─ Define communication between objects

Phase 1: OOP Fundamentals

Post 2: The Four Pillars of OOP

What You'll Learn:

• Overview of Encapsulation, Inheritance, Polymorphism, and Abstraction
• How the four pillars work together
• Real-world analogies for each concept
• Foundation for all OOP development

Key Concepts:

• Encapsulation: Bundle data and methods, hide internal state
• Inheritance: Create hierarchies, reuse code through "is-a" relationships
• Polymorphism: One interface, multiple implementations
• Abstraction: Hide complexity, expose essential features

Example Preview:

// Encapsulation - hiding internal details
class BankAccount {
  private balance: number = 0;
 
  public deposit(amount: number): void {
    if (amount > 0) this.balance += amount;
  }
 
  public getBalance(): number {
    return this.balance; // Controlled access
  }
}

Post 3: Classes, Objects, and Abstraction

What You'll Learn:

• Difference between classes (blueprints) and objects (instances)
• Abstract classes vs interfaces
• When to use abstraction
• Constructors, static members, access modifiers

Key Topics:

• Class definition and object instantiation
• Abstract classes (partial implementation)
• Interfaces (pure contracts)
• Access modifiers: public, private, protected
• Instance vs class members (static)

Example Preview:

// Abstraction with abstract class
abstract class Payment {
  constructor(public amount: number) {}
 
  abstract process(): void; // Must be implemented by subclasses
 
  printReceipt(): void {
    console.log(`Payment of $${this.amount} processed`);
  }
}
 
class CreditCardPayment extends Payment {
  process(): void {
    console.log("Processing credit card payment...");
  }
}
 
class PayPalPayment extends Payment {
  process(): void {
    console.log("Processing PayPal payment...");
  }
}

Post 4: Encapsulation and Information Hiding

What You'll Learn:

• Deep dive into encapsulation principles
• Getters and setters (when and why)
• Data validation and immutability
• Common encapsulation mistakes

Key Topics:

• Bundling data and methods together
• Information hiding (implementation details)
• Property decorators (Python @property, TypeScript get/set)
• Anemic domain model anti-pattern
• Protecting object invariants

Example Preview:

public class User {
  private String email;
  private int age;
 
  public void setEmail(String email) {
    if (!email.contains("@")) {
      throw new IllegalArgumentException("Invalid email");
    }
    this.email = email;
  }
 
  public void setAge(int age) {
    if (age < 0 || age > 120) {
      throw new IllegalArgumentException("Invalid age");
    }
    this.age = age;
  }
}

Benefits:

• Maintainability (change internal implementation without breaking clients)
• Flexibility (add validation logic later)
• Security (prevent invalid states)

Post 5: Inheritance and Composition

What You'll Learn:

• When to use inheritance ("is-a" relationships)
• When to use composition ("has-a" relationships)
• "Favor composition over inheritance" principle
• Avoiding inheritance pitfalls

Key Topics:

• Parent class (base/superclass) and child class (derived/subclass)
• Method overriding and super keyword
• Multi-level inheritance
• Composition and delegation patterns
• Mixins in TypeScript and Python
• Fragile base class problem

Example Preview:

// Inheritance - "is-a"
class Animal {
  constructor(public name: string) {}
  makeSound(): void {
    console.log("Some generic sound");
  }
}
 
class Dog extends Animal {
  makeSound(): void {
    console.log("Woof!");
  }
}
 
// Composition - "has-a"
class Engine {
  start(): void { console.log("Engine started"); }
}
 
class Car {
  private engine = new Engine(); // Composition
 
  start(): void {
    this.engine.start(); // Delegation
    console.log("Car ready to drive");
  }
}

When to Use Each:

• Inheritance: True "is-a" relationship (Dog is an Animal)
• Composition: "Has-a" relationship or behavior reuse (Car has an Engine)

Post 6: Polymorphism and Interfaces

What You'll Learn:

• Compile-time vs runtime polymorphism
• Polymorphism through interfaces
• Method overloading and overriding
• Liskov Substitution Principle introduction

Key Topics:

• Compile-time Polymorphism: Method overloading
• Runtime Polymorphism: Method overriding
• Interface contracts
• Multiple interface implementation
• Duck typing (Python, TypeScript)
• Abstract classes vs interfaces (detailed comparison)

Example Preview:

from abc import ABC, abstractmethod
 
# Interface-based polymorphism
class Shape(ABC):
    @abstractmethod
    def area(self) -> float:
        pass
 
class Circle(Shape):
    def __init__(self, radius: float):
        self.radius = radius
 
    def area(self) -> float:
        return 3.14159 * self.radius ** 2
 
class Rectangle(Shape):
    def __init__(self, width: float, height: float):
        self.width = width
        self.height = height
 
    def area(self) -> float:
        return self.width * self.height
 
# Polymorphic behavior
def print_area(shape: Shape):
    print(f"Area: {shape.area()}")
 
print_area(Circle(5))      # Works with Circle
print_area(Rectangle(4, 6)) # Works with Rectangle

Phase 2: SOLID Principles

Post 7: SOLID Principles Explained

What You'll Learn:

• All five SOLID principles in depth
• How SOLID relates to design patterns
• Refactoring code to follow SOLID
• Recognizing SOLID violations

The Five Principles:

1. Single Responsibility Principle (SRP)

• A class should have only one reason to change
• One class, one job

// ❌ BAD - Multiple responsibilities
class User {
  saveToDatabase(): void { /* DB logic */ }
  sendEmail(): void { /* Email logic */ }
  validateData(): void { /* Validation logic */ }
}
 
// ✅ GOOD - Separated responsibilities
class User {
  constructor(public name: string, public email: string) {}
}
 
class UserRepository {
  save(user: User): void { /* DB logic */ }
}
 
class EmailService {
  sendWelcomeEmail(user: User): void { /* Email logic */ }
}
 
class UserValidator {
  validate(user: User): boolean { /* Validation logic */ }
}

2. Open/Closed Principle (OCP)

• Open for extension, closed for modification
• Add new functionality without changing existing code

3. Liskov Substitution Principle (LSP)

• Subtypes must be substitutable for base types
• Child classes shouldn't break parent class contracts

4. Interface Segregation Principle (ISP)

• Clients shouldn't depend on interfaces they don't use
• Many small interfaces > one large interface

5. Dependency Inversion Principle (DIP)

• Depend on abstractions, not concretions
• High-level modules shouldn't depend on low-level modules

Why SOLID Matters:

• Makes code easier to maintain
• Improves testability
• Enables clean architecture
• Foundation for design patterns

Phase 3: Creational Patterns

Creational patterns deal with object creation mechanisms.

Post 8: Singleton Pattern

What You'll Learn:

• Ensure only one instance of a class exists
• Thread-safe Singleton implementations
• Singleton anti-pattern debate
• Alternatives to Singleton (Dependency Injection)

Use Cases:

• Logger
• Configuration manager
• Database connection pool
• Cache manager

Example Preview:

public class DatabaseConnection {
  private static DatabaseConnection instance;
 
  private DatabaseConnection() {
    // Private constructor
  }
 
  public static synchronized DatabaseConnection getInstance() {
    if (instance == null) {
      instance = new DatabaseConnection();
    }
    return instance;
  }
}

Pros & Cons:

• ✅ Controlled access to sole instance
• ✅ Reduced memory footprint
• ❌ Global state (testing difficulty)
• ❌ Violates Single Responsibility Principle
• ❌ Hides dependencies

Post 9: Factory and Abstract Factory Patterns

What You'll Learn:

• Simple Factory pattern
• Factory Method pattern
• Abstract Factory pattern
• When to use each variant

Use Cases:

• Object creation based on input
• Plugin architectures
• Cross-platform UI components
• Payment processor selection

Example Preview:

// Factory Method Pattern
interface IDocument {
  open(): void;
  save(): void;
}
 
abstract class Application {
  abstract createDocument(): IDocument;
 
  newDocument(): void {
    const doc = this.createDocument(); // Factory method
    doc.open();
  }
}
 
class PDFApplication extends Application {
  createDocument(): IDocument {
    return new PDFDocument();
  }
}
 
class WordApplication extends Application {
  createDocument(): IDocument {
    return new WordDocument();
  }
}

Post 10: Builder Pattern

What You'll Learn:

• Construct complex objects step by step
• Fluent interface (method chaining)
• Avoid telescoping constructor anti-pattern
• Director pattern (optional)

Use Cases:

• Complex object construction with many optional parameters
• HTTP request builders
• SQL query builders
• Configuration objects

Example Preview:

class HttpRequest {
  private constructor(
    public url: string,
    public method: string,
    public headers: Map<string, string>,
    public body?: string
  ) {}
 
  static builder(): HttpRequestBuilder {
    return new HttpRequestBuilder();
  }
}
 
class HttpRequestBuilder {
  private url!: string;
  private method: string = 'GET';
  private headers = new Map<string, string>();
  private body?: string;
 
  setUrl(url: string): HttpRequestBuilder {
    this.url = url;
    return this; // Method chaining
  }
 
  setMethod(method: string): HttpRequestBuilder {
    this.method = method;
    return this;
  }
 
  addHeader(key: string, value: string): HttpRequestBuilder {
    this.headers.set(key, value);
    return this;
  }
 
  setBody(body: string): HttpRequestBuilder {
    this.body = body;
    return this;
  }
 
  build(): HttpRequest {
    return new HttpRequest(this.url, this.method, this.headers, this.body);
  }
}
 
// Usage - fluent interface
const request = HttpRequest.builder()
  .setUrl("https://api.example.com/users")
  .setMethod("POST")
  .addHeader("Content-Type", "application/json")
  .setBody(JSON.stringify({ name: "John" }))
  .build();

Post 11: Prototype Pattern

What You'll Learn:

• Clone objects efficiently
• Shallow copy vs deep copy
• Prototype registry
• When object creation is expensive

Use Cases:

• Game object spawning (cloning enemies)
• Document templates
• Configuration presets
• Copying complex objects

Phase 4: Structural Patterns

Structural patterns deal with object composition and relationships.

Post 12: Adapter and Facade Patterns

What You'll Learn:

• Adapter: Make incompatible interfaces work together
• Facade: Simplify complex subsystems with unified interface
• When to use each

Adapter Use Cases:

• Integrating third-party libraries
• Legacy system integration
• Multiple payment provider adapters

Facade Use Cases:

• Simplifying complex libraries
• Hiding subsystem complexity
• Order processing workflow

Example Preview:

// Adapter Pattern - make incompatible interfaces compatible
interface IModernPayment {
  processPayment(amount: number): void;
}
 
class LegacyPaymentSystem {
  makePayment(dollars: number, cents: number): void {
    console.log(`Legacy: $${dollars}.${cents}`);
  }
}
 
class PaymentAdapter implements IModernPayment {
  constructor(private legacy: LegacyPaymentSystem) {}
 
  processPayment(amount: number): void {
    const dollars = Math.floor(amount);
    const cents = Math.round((amount - dollars) * 100);
    this.legacy.makePayment(dollars, cents);
  }
}
 
// Facade Pattern - simplify complex subsystem
class OrderFacade {
  private paymentService = new PaymentService();
  private inventoryService = new InventoryService();
  private shippingService = new ShippingService();
 
  placeOrder(order: Order): void {
    // Simple interface hiding complexity
    this.inventoryService.checkStock(order);
    this.paymentService.charge(order);
    this.shippingService.ship(order);
  }
}

Post 13: Decorator and Proxy Patterns

What You'll Learn:

• Decorator: Add behavior dynamically without modifying original
• Proxy: Control access to objects
• Virtual proxy, Protection proxy, Caching proxy

Decorator Use Cases:

• Adding features to objects at runtime
• Coffee shop example (add milk, sugar, etc.)
• Stream decorators (buffering, compression)
• Middleware pattern

Proxy Use Cases:

• Lazy loading (Virtual Proxy)
• Access control (Protection Proxy)
• Caching expensive operations
• Logging and monitoring

Example Preview:

# Decorator Pattern
class Coffee:
    def cost(self) -> float:
        return 5.0
 
    def description(self) -> str:
        return "Simple coffee"
 
class MilkDecorator:
    def __init__(self, coffee: Coffee):
        self._coffee = coffee
 
    def cost(self) -> float:
        return self._coffee.cost() + 2.0
 
    def description(self) -> str:
        return self._coffee.description() + ", milk"
 
# Usage - stack decorators
coffee = Coffee()
coffee = MilkDecorator(coffee)
coffee = SugarDecorator(coffee)
print(coffee.description())  # "Simple coffee, milk, sugar"
print(coffee.cost())          # 9.0

Phase 5: Behavioral Patterns

Behavioral patterns deal with object communication and responsibilities.

Post 14: Strategy and Template Method Patterns

What You'll Learn:

• Strategy: Swap algorithms at runtime
• Template Method: Define algorithm skeleton, let subclasses customize steps
• Eliminating conditional complexity

Strategy Use Cases:

• Payment method selection
• Sorting algorithms
• Compression strategies
• Navigation methods (car, bike, walk)

Template Method Use Cases:

• Data parsers (CSV, JSON, XML)
• Beverage preparation (tea, coffee)
• Order processing workflows

Example Preview:

// Strategy Pattern
interface PaymentStrategy {
    void pay(int amount);
}
 
class CreditCardStrategy implements PaymentStrategy {
    public void pay(int amount) {
        System.out.println("Paid $" + amount + " with credit card");
    }
}
 
class PayPalStrategy implements PaymentStrategy {
    public void pay(int amount) {
        System.out.println("Paid $" + amount + " with PayPal");
    }
}
 
class ShoppingCart {
    private PaymentStrategy paymentStrategy;
 
    public void setPaymentStrategy(PaymentStrategy strategy) {
        this.paymentStrategy = strategy;
    }
 
    public void checkout(int amount) {
        paymentStrategy.pay(amount); // Runtime algorithm selection
    }
}
 
// Usage
ShoppingCart cart = new ShoppingCart();
cart.setPaymentStrategy(new CreditCardStrategy());
cart.checkout(100);
 
cart.setPaymentStrategy(new PayPalStrategy());
cart.checkout(200);

Post 15: Observer, Command, and State Patterns

What You'll Learn:

• Observer: One-to-many dependency (Pub-Sub)
• Command: Encapsulate requests as objects (undo/redo)
• State: Change behavior when internal state changes

Observer Use Cases:

• Event systems
• Newsletter subscriptions
• Stock price monitoring
• UI updates (MVC pattern)

Command Use Cases:

• Undo/redo operations
• Task queues
• Transaction systems
• Remote controls

State Use Cases:

• Document workflow (Draft → Review → Published)
• Order status (Pending → Shipped → Delivered)
• TCP connections
• Vending machines

Example Preview:

// Observer Pattern
interface Observer {
  update(data: any): void;
}
 
class Subject {
  private observers: Observer[] = [];
 
  attach(observer: Observer): void {
    this.observers.push(observer);
  }
 
  notify(data: any): void {
    this.observers.forEach(obs => obs.update(data));
  }
}
 
class Newsletter extends Subject {
  publishPost(title: string): void {
    console.log(`New post: ${title}`);
    this.notify(title); // Notify all subscribers
  }
}
 
class EmailSubscriber implements Observer {
  constructor(private email: string) {}
 
  update(title: string): void {
    console.log(`Email to ${this.email}: New post "${title}"`);
  }
}
 
// Usage
const newsletter = new Newsletter();
newsletter.attach(new EmailSubscriber("user1@example.com"));
newsletter.attach(new EmailSubscriber("user2@example.com"));
newsletter.publishPost("Learning Design Patterns"); // Both notified

Learning Path Recommendations

For Complete Beginners (12-16 weeks)

Path: Linear progression through all phases

1. Weeks 1-2: Post 2 (Four Pillars of OOP)
2. Weeks 3-6: Posts 3-6 (OOP Fundamentals)
3. Weeks 7-8: Post 7 (SOLID Principles)
4. Weeks 9-11: Posts 8-10 (Creational Patterns - focus on Singleton, Factory, Builder)
5. Weeks 12-13: Posts 12-13 (Structural Patterns)
6. Weeks 14-16: Posts 14-15 (Behavioral Patterns)

Practice:

• Implement each pattern in a small project
• Refactor existing code to apply patterns
• Build a final project using multiple patterns

For Interview Prep (4 weeks, intensive)

Focus on most commonly asked patterns:

Week 1: OOP Fundamentals + SOLID

• Post 2 (Four Pillars)
• Post 7 (SOLID Principles)

Week 2: Creational Patterns

• Post 8 (Singleton)
• Post 9 (Factory)
• Post 10 (Builder)

Week 3: Structural + Behavioral

• Post 12 (Adapter/Facade)
• Post 14 (Strategy/Template Method)

Week 4: Practice + Mock Interviews

• Implement patterns from scratch
• Explain design decisions
• Review common interview questions

For Self-Taught Developers (8 weeks)

Path: Focus on filling knowledge gaps

Week 1: OOP Pillars

• Post 2 (Four Pillars overview)

Weeks 2-3: SOLID (Most Important)

• Post 7 (SOLID Principles) - Deep study

Weeks 4-5: Essential Patterns

• Post 9 (Factory)
• Post 14 (Strategy)
• Post 15 (Observer)

Weeks 6-7: Structural Patterns

• Post 12 (Adapter/Facade)
• Post 13 (Decorator/Proxy)

Week 8: Practice and Review

• Refactor personal projects
• Identify patterns in open-source code

For Experienced Developers (4-6 weeks)

Path: Deepen expertise, focus on advanced patterns

Week 1: Review SOLID

• Post 7 (SOLID Principles) - Focus on violations in your code

Weeks 2-3: Behavioral Patterns (Most Complex)

• Post 14 (Strategy/Template Method)
• Post 15 (Observer/Command/State)

Weeks 4-5: Structural Patterns

• Post 13 (Decorator/Proxy) - Advanced techniques

Week 6: Architecture

• Apply patterns to real projects
• Study anti-patterns and over-engineering

Common Misconceptions About OOP

Misconception 1: "OOP is always better than procedural/functional"

Reality: Each paradigm has its place.

• OOP: Great for modeling real-world entities, complex systems
• Procedural: Better for simple scripts, data transformations
• Functional: Excellent for data pipelines, immutability needs

Use the right tool for the job.

Misconception 2: "More design patterns = better code"

Reality: Over-engineering is a real problem.

❌ Bad: Using Singleton for everything ❌ Bad: Creating factories when simple constructors suffice ❌ Bad: Adding abstraction layers "just in case"

✅ Good: Apply patterns when they solve real problems ✅ Good: Keep it simple until complexity demands patterns ✅ Good: Refactor to patterns when pain points emerge

YAGNI: You Aren't Gonna Need It

Misconception 3: "Inheritance is the best way to reuse code"

Reality: Composition is often better.

Problems with Inheritance:

• Tight coupling
• Fragile base class problem
• Deep hierarchies are hard to understand
• Violates "favor composition over inheritance"

When to Use Inheritance:

• True "is-a" relationship
• Shared behavior + shared state
• Liskov Substitution Principle holds

When to Use Composition:

• "Has-a" relationship
• Flexible behavior combination
• Avoiding deep hierarchies

How to Practice OOP and Design Patterns

1. Refactor Existing Code

Take procedural code and refactor it using OOP principles:

Before (Procedural):

def calculate_discount(price, customer_type):
    if customer_type == "regular":
        return price * 0.9
    elif customer_type == "premium":
        return price * 0.8
    elif customer_type == "vip":
        return price * 0.7
    return price

After (Strategy Pattern):

from abc import ABC, abstractmethod
 
class DiscountStrategy(ABC):
    @abstractmethod
    def calculate(self, price: float) -> float:
        pass
 
class RegularDiscount(DiscountStrategy):
    def calculate(self, price: float) -> float:
        return price * 0.9
 
class PremiumDiscount(DiscountStrategy):
    def calculate(self, price: float) -> float:
        return price * 0.8
 
class VIPDiscount(DiscountStrategy):
    def calculate(self, price: float) -> float:
        return price * 0.7
 
class Customer:
    def __init__(self, discount_strategy: DiscountStrategy):
        self.discount_strategy = discount_strategy
 
    def get_price(self, price: float) -> float:
        return self.discount_strategy.calculate(price)

2. Build Small Projects

E-commerce System:

• Use Factory for product creation
• Use Strategy for payment methods
• Use Observer for order notifications
• Use Decorator for product options

Document Editor:

• Use Command for undo/redo
• Use Composite for document structure
• Use Observer for auto-save
• Use Memento for version history

Game Development:

• Use Prototype for enemy spawning
• Use State for character behavior
• Use Singleton for game manager
• Use Factory for level generation

3. Study Open-Source Code

Spring Framework (Java):

• Dependency Injection (DIP)
• Factory pattern everywhere
• Singleton scope for beans
• Proxy for AOP
• Template Method in JdbcTemplate

React (JavaScript):

• Component composition
• HOC pattern (Decorator)
• Render props (Strategy)
• Context API (Observer-like)

Django (Python):

• MVC/MTV architecture
• Manager pattern (Facade)
• Middleware (Chain of Responsibility)
• ORM (Active Record)

4. Code Review Practice

Review code (yours or others) and ask:

• Are SOLID principles followed?
• Can design patterns simplify this?
• Is there unnecessary complexity?
• Are abstractions hiding or exposing complexity?

Anti-Patterns to Avoid

1. God Class (Violates SRP)

Problem: One class does everything.

// ❌ BAD - God class
class User {
  login() {}
  logout() {}
  saveToDatabase() {}
  sendEmail() {}
  validateInput() {}
  generateReport() {}
  processPayment() {}
  uploadFile() {}
}

Solution: Separate concerns into multiple classes.

2. Anemic Domain Model

Problem: Classes with only getters/setters, no behavior.

// ❌ BAD - Anemic model
class Order {
    private List<Item> items;
    public List<Item> getItems() { return items; }
    public void setItems(List<Item> items) { this.items = items; }
}
 
// Business logic scattered elsewhere
class OrderService {
    public double calculateTotal(Order order) {
        // Logic that should be in Order class
    }
}

Solution: Put behavior in domain objects.

// ✅ GOOD - Rich domain model
class Order {
    private List<Item> items;
 
    public double calculateTotal() {
        return items.stream()
            .mapToDouble(Item::getPrice)
            .sum();
    }
 
    public void addItem(Item item) {
        this.items.add(item);
    }
}

3. Overusing Patterns

Problem: Applying patterns unnecessarily.

// ❌ BAD - Overkill for simple case
class StringFactory {
  static createString(value: string): String {
    return new String(value);
  }
}
 
// ✅ GOOD - Just use the language
const str = "Hello, World!";

Rule: Apply patterns only when they solve real problems.

Resources and Next Steps

Books

Essential:

• "Design Patterns: Elements of Reusable Object-Oriented Software" (Gang of Four) - The classic
• "Head First Design Patterns" by Freeman et al. - Beginner-friendly
• "Clean Code" by Robert C. Martin - SOLID principles

Advanced:

• "Refactoring: Improving the Design of Existing Code" by Martin Fowler
• "Design Patterns Explained" by Alan Shalloway

Online Resources

• Refactoring.Guru - Excellent visual explanations
• SourceMaking - Comprehensive catalog
• SOLID Principles Guide

What's Next?

Start with Post 2: The Four Pillars of OOP to build your foundation, then progress through the series based on your learning path.

Summary

This comprehensive roadmap covers 15 posts organized into 5 phases:

Phase 1: OOP Fundamentals (4 pillars, classes, objects, encapsulation, inheritance, polymorphism) Phase 2: SOLID Principles (5 principles for clean OOP) Phase 3: Creational Patterns (Singleton, Factory, Builder, Prototype) Phase 4: Structural Patterns (Adapter, Facade, Decorator, Proxy) Phase 5: Behavioral Patterns (Strategy, Template Method, Observer, Command, State)

By completing this series, you'll be able to:

• ✅ Think in objects and design maintainable systems
• ✅ Apply SOLID principles in daily coding
• ✅ Recognize when to apply design patterns
• ✅ Implement 11+ design patterns from memory
• ✅ Refactor procedural code to OOP
• ✅ Pass OOP/design pattern interview questions
• ✅ Read and understand enterprise codebases

Ready to begin? Start with Post 2: The Four Pillars of OOP!

Questions or feedback? Feel free to reach out at contact@chanhle.dev or connect with me on X.

Happy coding! 🚀