What are some examples of the decorator pattern in different programming languages?

What are some examples of the decorator pattern 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. In Python, for instance, decorators are often used to modify functions or methods. In Java, you might use the decorator pattern to add responsibilities to objects at runtime.

Can you give me a specific example in Python?

Sure! In Python, you can create a simple logging decorator like this:

def logger(func):
    def wrapper(*args, **kwargs):
        print(f'Calling {func.__name__}')
        return func(*args, **kwargs)
    return wrapper

@logger
def add(a, b):
    return a + b

When you call add(2, 3), it will print 'Calling add' before returning the result.

What about an example in Java?

In Java, you can implement the decorator pattern using interfaces. For example:

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

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

class MilkDecorator implements Coffee {
    private Coffee coffee;

    public MilkDecorator(Coffee coffee) {
        this.coffee = coffee;
    }

    public String getDescription() {
        return coffee.getDescription() + ", milk";
    }
    public double cost() {
        return coffee.cost() + 0.50;
    }
}

Here, MilkDecorator adds functionality to SimpleCoffee.