design-patterns-implementation

Design Patterns Implementation

Overview

Apply proven design patterns to create maintainable, extensible, and testable code architectures.

When to Use

• Solving common architectural problems
• Making code more maintainable and testable
• Implementing extensible plugin systems
• Decoupling components
• Following SOLID principles
• Code reviews identifying architectural issues

Common Design Patterns

1. Singleton Pattern

Ensure a class has only one instance with global access.

class DatabaseConnection {
  private static instance: DatabaseConnection;
  private connection: any;

  private constructor() {
    this.connection = this.createConnection();
  }

  public static getInstance(): DatabaseConnection {
    if (!DatabaseConnection.instance) {
      DatabaseConnection.instance = new DatabaseConnection();
    }
    return DatabaseConnection.instance;
  }

  private createConnection() {
    return { /* connection logic */ };
  }
}

// Usage
const db1 = DatabaseConnection.getInstance();
const db2 = DatabaseConnection.getInstance();
// db1 === db2 (same instance)

2. Factory Pattern

Create objects without specifying exact classes.

from abc import ABC, abstractmethod

class PaymentProcessor(ABC):
    @abstractmethod
    def process_payment(self, amount: float) -> bool:
        pass

class StripeProcessor(PaymentProcessor):
    def process_payment(self, amount: float) -> bool:
        # Stripe-specific logic
        return True

class PayPalProcessor(PaymentProcessor):
    def process_payment(self, amount: float) -> bool:
        # PayPal-specific logic
        return True

class PaymentProcessorFactory:
    @staticmethod
    def create_processor(processor_type: str) -> PaymentProcessor:
        if processor_type == 'stripe':
            return StripeProcessor()
        elif processor_type == 'paypal':
            return PayPalProcessor()
        else:
            raise ValueError(f'Unknown processor: {processor_type}')

# Usage
processor = PaymentProcessorFactory.create_processor('stripe')
processor.process_payment(100.00)