Summary of "7 Design Patterns EVERY Developer Should Know"

Summary of “7 Design Patterns EVERY Developer Should Know”

This video by Forest introduces seven fundamental software design patterns that help solve common programming problems across languages and platforms. These patterns are widely used because they improve code organization, flexibility, and maintainability. The video references the seminal 1994 Gang of Four book, which cataloged 23 design patterns grouped into three categories: creational, structural, and behavioral. Forest covers seven key patterns across these categories with explanations, analogies, code examples, and practical advice.

Main Ideas and Concepts

Design Patterns: Reusable solutions to common software design problems.
Gang of Four Book: Foundation of design patterns, categorizing 23 patterns into:
- Creational Patterns: Object creation mechanisms.
- Structural Patterns: How objects relate and compose.
- Behavioral Patterns: How objects communicate and interact.

Detailed Breakdown of the 7 Patterns Covered

1. Singleton Pattern (Creational)

Ensures a class has only one instance and provides a global access point.
Example: Centralized logging system to avoid multiple conflicting loggers.
Benefits:
- Guarantees a single instance.
- Global access simplifies usage.
Drawbacks:
- Difficult to test/mock.
- Requires thread safety in multi-threaded environments.
- Considered a glorified global variable; use sparingly.
Use when: A single shared resource (like a DB connection pool or logger) is needed.

2. Builder Pattern (Creational)

Helps construct complex objects step-by-step, especially with many optional parameters.
Allows chaining method calls for clarity and flexibility.
Example: Building an HTTP request with headers, query params, body, etc.
Benefits:
- Improves code readability.
- Easy to extend with new options.
Drawbacks:
- More upfront code to write.
Use when: Constructors have many parameters or when object creation is complex and incremental.

3. Factory Pattern (Creational)

Encapsulates object creation logic in a separate factory class.
Example: Creating different user types (admin, moderator, regular user) without scattering new calls.
Benefits:
- Centralizes creation logic.
- Makes code more maintainable and flexible.
Drawbacks:
- Adds an abstraction layer.
- Factory class can become tightly coupled.
Use when: You find yourself using new repeatedly to create objects.

4. Facade Pattern (Structural)

Provides a simplified interface to a complex subsystem.
Example: A single OrderFacade hides payment processing, inventory checks, fraud detection.
Benefits:
- Simplifies client code.
- Encapsulates complexity.
Drawbacks:
- Risk of creating a “god object” that knows too much and does too much.
Use when: You have complex subsystems that need to be simplified for client code.

5. Adapter Pattern (Structural)

Converts the interface of one class into another expected by clients.
Example: Wrapping a third-party weather API that returns Celsius and km/h to provide Fahrenheit and mph.
Benefits:
- Enables integration of incompatible interfaces.
- Keeps conversion logic in one place.
Drawbacks:
- Can become tedious if many adapters are needed.
Use when: Integrating third-party libraries or APIs that don’t match your app’s interface.

6. Strategy Pattern (Behavioral)

Defines a family of interchangeable algorithms encapsulated in separate classes.
Example: Different commuting strategies like driving, biking, or taking the bus.
Benefits:
- Avoids large if-else chains.
- Supports open/closed principle (add new strategies without modifying existing code).
Drawbacks:
- Introduces many small classes.
Use when: You have multiple ways to perform the same action and want to swap them easily.

7. Observer Pattern (Behavioral)

Allows objects (observers) to subscribe and get notified automatically when another object (subject) changes.
Example: YouTube subscribers getting notified when a new video is uploaded.
Benefits:
- Decouples event producers and consumers.
- Efficient notification system.
Drawbacks:
- Can lead to “event callback hell” if overused or poorly managed.
Use when: Event-driven programming, monitoring, or any publish-subscribe scenario.

Additional Notes

The video includes practical analogies (e.g., Lego blocks for structural patterns, commuting for strategy).
Emphasizes that design patterns are good programming techniques, not just abstract concepts.
Encourages learning and practicing these patterns to internalize their use.
Mentions a sponsor, TwinGate, a modern secure remote access solution (not a VPN).

Speakers and Sources

Forest: Main speaker and presenter of the video.
Gang of Four (Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides): Authors of the foundational design patterns book referenced.
Sponsor: TwinGate: Mentioned as a sponsor and example of managing complexity.

Summary

This video is a comprehensive beginner-to-intermediate introduction to 7 essential design patterns:

Singleton
Builder
Factory
Facade
Adapter
Strategy
Observer

It explains what problems they solve, how they work, when to use them, and their pros and cons, all illustrated with relatable examples and analogies.