Decorator - a structural design pattern in object-oriented programming, allowing dynamically adding new functionality or altering the behavior of existing objects without changing their code. This is achieved by creating a new class that wraps the original object and provides it with additional capabilities.
The main components of the decorator include:
* Interface class: Defines the basic interface for components.
* Base class: Implements the core functionality.
* Decorator: Contains a reference to the component and implements the same interface as the component. Adds or modifies the component's functionality.
* Concrete decorator class: Implements specific changes to functionality.
<?php
// Component interface
interface Component {
public function operation(): string;
}
// Base class
class ConcreteComponent implements Component {
public function operation(): string {
return "ConcreteComponent: base operation\n";
}
}
// Decorator
class Decorator implements Component {
protected $component;
public function __construct(Component $component) {
$this->component = $component;
}
public function operation(): string {
return $this->component->operation();
}
}
// Concrete decorator
class ConcreteDecoratorA extends Decorator {
public function operation(): string {
return "ConcreteDecoratorA(" . parent::operation() . "): additional functionality\n";
}
}
// Concrete decorator
class ConcreteDecoratorB extends Decorator {
public function operation(): string {
return "ConcreteDecoratorB(" . parent::operation() . "): additional functionality\n";
}
}
// Client code
function clientCode(Component $component) {
echo "RESULT: " . $component->operation();
}
// Example usage
$simple = new ConcreteComponent();
echo "Client: I can work with the simple component:\n";
clientCode($simple);
echo "\n";
$decorator1 = new ConcreteDecoratorA($simple);
$decorator2 = new ConcreteDecoratorB($decorator1);
echo "Client: Now I can combine decorators:\n";
clientCode($decorator2);
?>
