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Design Patterns Guide

Overview

Design patterns are typical solutions to common problems in software design. Each pattern is like a blueprint that you can customize to solve a particular design problem in your code.

Pattern Categories

🏭 Creational Patterns

Provide object creation mechanisms that increase flexibility and reuse of existing code.

Factory Method
Abstract Factory
Builder
Prototype
Singleton

🔨 Structural Patterns

Explain how to assemble objects and classes into larger structures while keeping these structures flexible and efficient.

Adapter
Bridge
Composite
Decorator
Facade
Flyweight
Proxy

🎭 Behavioral Patterns

Take care of effective communication and the assignment of responsibilities between objects.

Chain of Responsibility
Command
Iterator
Mediator
Memento
Observer
State
Strategy
Template Method
Visitor

Pattern Selection Guide

When to Use Creational Patterns

Need to create objects without exposing creation logic
Want to create objects based on certain conditions
Need to reuse existing objects instead of creating new ones
Want to create complex objects step by step

When to Use Structural Patterns

Need to ensure that classes work together despite incompatible interfaces
Want to simplify complex subsystem interfaces
Need to add responsibilities to objects dynamically
Want to optimize resource usage with shared objects

When to Use Behavioral Patterns

Need flexible communication between objects
Want to define algorithms that can be easily swapped
Need to implement complex workflows or state transitions
Want to define a skeleton of an algorithm with customizable parts

Best Practices

Pattern Implementation

Understand the Problem
- Clearly identify the issue you’re trying to solve
- Consider if a pattern is really needed
- Evaluate multiple pattern options
Keep It Simple
- Don’t force patterns where they’re not needed
- Start with the simplest solution
- Refactor to patterns when complexity justifies it
Consider Maintenance
- Document pattern usage clearly
- Explain the rationale for choosing the pattern
- Consider the impact on testing

Common Anti-Patterns to Avoid

Pattern Overuse
- Using patterns without clear benefits
- Overcomplicating simple solutions
- Mixing too many patterns
Incorrect Pattern Application
- Using patterns in wrong contexts
- Not following pattern principles
- Partial pattern implementation
Inflexible Implementation
- Hard-coding pattern components
- Not considering future changes
- Tightly coupling pattern elements

Pattern Relationships

graph TD
    A[Creational Patterns] --> B[Factory Method]
    A --> C[Abstract Factory]
    A --> D[Builder]
    A --> E[Prototype]
    A --> F[Singleton]
    
    G[Structural Patterns] --> H[Adapter]
    G --> I[Bridge]
    G --> J[Composite]
    G --> K[Decorator]
    G --> L[Facade]
    G --> M[Flyweight]
    G --> N[Proxy]
    
    O[Behavioral Patterns] --> P[Chain of Responsibility]
    O --> Q[Command]
    O --> R[Iterator]
    O --> S[Mediator]
    O --> T[Observer]
    O --> U[State]
    O --> V[Strategy]
    O --> W[Template Method]
    O --> X[Visitor]