What is the decorator pattern and how is it implemented in different programming languages?

What is the decorator pattern and how is it implemented in different programming languages?

The decorator pattern is a structural design pattern that allows behavior to be added to individual objects, either statically or dynamically, without affecting the behavior of other objects from the same class. It is commonly used in languages like Python, Java, and JavaScript.

Can you give me an example of the decorator pattern in Python?

Sure! In Python, you can use decorators to modify the behavior of a function. Here's a simple example:

def my_decorator(func):
    def wrapper():
        print("Something is happening before the function is called.")
        func()
        print("Something is happening after the function is called.")
    return wrapper

@my_decorator
def say_hello():
    print("Hello!")

say_hello()

How about in Java? Can you show me a Java example?

Certainly! In Java, you can implement the decorator pattern using interfaces and classes. Here's a basic example:

interface Coffee {
    String getDescription();
    double cost();
}

class SimpleCoffee implements Coffee {
    public String getDescription() {
        return "Simple coffee";
    }
    public double cost() {
        return 1.00;
    }
}

abstract class CoffeeDecorator implements Coffee {
    protected Coffee coffee;
    public CoffeeDecorator(Coffee coffee) {
        this.coffee = coffee;
    }
}

class MilkDecorator extends CoffeeDecorator {
    public MilkDecorator(Coffee coffee) {
        super(coffee);
    }
    public String getDescription() {
        return coffee.getDescription() + ", milk";
    }
    public double cost() {
        return coffee.cost() + 0.50;
    }
}

Coffee coffee = new SimpleCoffee();
coffee = new MilkDecorator(coffee);
System.out.println(coffee.getDescription() + " costs " + coffee.cost());