Purpose
Recognize when to apply established design patterns to create flexible, maintainable, and reusable code structures.
When to Use
- •Designing class structures
- •Solving recurring design problems
- •Refactoring complex code
- •Planning extensible architectures
Key Capabilities
- •Pattern Recognition - Identify when patterns apply
- •Pattern Implementation - Correctly implement chosen patterns
- •Trade-off Analysis - Understand pattern costs and benefits
Common Patterns
- •Creational: Factory, Builder, Singleton
- •Structural: Adapter, Decorator, Facade
- •Behavioral: Observer, Strategy, Command
Example - Strategy Pattern
python
# Problem: Multiple payment methods with different processing logic
class PaymentStrategy:
def process(self, amount): pass
class CreditCardPayment(PaymentStrategy):
def process(self, amount):
# Credit card processing logic
print(f"Processing ${amount} via credit card")
class PayPalPayment(PaymentStrategy):
def process(self, amount):
# PayPal processing logic
print(f"Processing ${amount} via PayPal")
class Order:
def __init__(self, payment_strategy: PaymentStrategy):
self.payment = payment_strategy
def checkout(self, amount):
self.payment.process(amount)
# Usage
order1 = Order(CreditCardPayment())
order1.checkout(100)
order2 = Order(PayPalPayment())
order2.checkout(50)
Best Practices
- •✅ Use patterns to solve actual problems, not for their own sake
- •✅ Understand the problem before applying a pattern
- •✅ Keep it simple - don't over-engineer
- •❌ Avoid: Using patterns you don't fully understand
- •❌ Avoid: Forcing patterns where they don't fit