Decorator

Añade funcionalidad adicional a un objeto dinámicamente. Proporciona una alternativa para subclasificar por extensión de funcionalidad.

abstract class Component
{
  // Methods
  abstract public void Operation();
}

// "ConcreteComponent"
class ConcreteComponent : Component
{
  // Methods
  override public void Operation()
  {
     Console.WriteLine("ConcreteComponent.Operation()");
  }
}

// "Decorator"
abstract class Decorator : Component
{
   // Fields
   protected Component component;
   
   // Methods
   public void SetComponent( Component component )
   {
      this.component = component;
   }

   override public void Operation()
   {
      if( component != null )
         component.Operation();
   }
}

// "ConcreteDecoratorA"
class ConcreteDecoratorA : Decorator
{
   // Fields
   private string addedState;
   
   // Methods
   override public void Operation()
   {
     base.Operation();
     addedState = "new state";
     Console.WriteLine("ConcreteDecoratorA.Operation()");
   }
}

// "ConcreteDecoratorB"
class ConcreteDecoratorB : Decorator
{
  // Methods
  override public void Operation()
  {
     base.Operation();
     AddedBehavior();
     Console.WriteLine("ConcreteDecoratorB.Operation()");
  }

  void AddedBehavior()
  {
  }
}

/// Client test
public class Client
{
    public static void Main( string[] args )
    {
      // Create ConcreteComponent and two Decorators
      ConcreteComponent c = new ConcreteComponent();
      ConcreteDecoratorA d1 = new ConcreteDecoratorA();
      ConcreteDecoratorB d2 = new ConcreteDecoratorB();
      
      // Link decorators
      d1.SetComponent( c );
      d2.SetComponent( d1 );
      d2.Operation();
    }
}