Decorator Pattern

Introduction

The Decorator Pattern is a structural design pattern that enables behavior to be added to individual objects, either statically or dynamically, without affecting the behavior of other objects from the same class.

Key Concepts

• Component: An interface or abstract class defining the operations that can be dynamically added to concrete components.
• Concrete Component: The original object to which additional responsibilities can be attached.
• Decorator: A class that implements the same interface as the component and has a reference to a component object. It can add behavior to the component.

Implementation

Here's a step-by-step implementation of the Decorator Pattern in Python.

class Coffee:
    def cost(self):
        return 5

class MilkDecorator:
    def __init__(self, coffee):
        self._coffee = coffee

    def cost(self):
        return self._coffee.cost() + 1

class SugarDecorator:
    def __init__(self, coffee):
        self._coffee = coffee

    def cost(self):
        return self._coffee.cost() + 0.5

# Usage
coffee = Coffee()
print("Cost of plain coffee: $", coffee.cost())

milk_coffee = MilkDecorator(coffee)
print("Cost of coffee with milk: $", milk_coffee.cost())

sugar_milk_coffee = SugarDecorator(milk_coffee)
print("Cost of coffee with milk and sugar: $", sugar_milk_coffee.cost())
        

Best Practices

• Favor composition over inheritance.
• Keep decorators focused on a single responsibility.
• Use decorators to adhere to the Open/Closed Principle (open for extension, closed for modification).

FAQ