Decorator Pattern

Decorator ist ein strukturelles Entwurfsmuster, mit dem du neue Verhaltensweisen an Objekte anhängen kannst, indem du diese Objekte in speziellen Wrapper-Objekten platzierst, die die Verhaltensweisen enthalten.

Klassendiagramm

Implementierung

Client

Client.cs

Component component = new ConcreteDecorator2(
    component: new ConcreteDecorator1(
        component: new ConcreteDecorator1(
            component: new ConcreteComponent())));

component.Operation();

Component

IComponent.cs

public interface IComponent
{
    void Operation();
}

ConcreteComponent

ConcreteComponent.cs

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

Decorator

Decorator.cs

public abstract class Decorator(Component component) : Component
{
    protected Component _component = component;

    public virtual void Operation()
    {
        _component.Operation();
    }
}

ConcreteDecorator1

ConcreteDecorator1.cs

public abstract class Decorator(Component component) : Component
{
    protected Component _component = component;

    public virtual void Operation()
    {
        _component.Operation();
    }
}

ConcreteDecorator2

ConcreteDecorator2.cs

public class ConcreteDecorator2(Component component) : Decorator(component)
{
    public override void Operation()
    {
        Console.WriteLine("-------- Concrete Decorator 2 -----------");
        _component.Operation();
        Console.WriteLine("-------- Concrete Decorator 2 -----------");
    }
}

Beispiele

Klassendiagramme

Implementierung

Client

ITeslaModel3 car = new LongRangeTeslaDecorator(
    car: new RedPaintTeslaDecorator(
        car: new BasicTeslaModel3()));

Console.WriteLine($"Description: {car.GetDescription()}");
Console.WriteLine($"Price: {car.GetPrice()}");
Console.WriteLine($"Range: {car.GetRange()}");

Component

public interface ITeslaModel3
{
    decimal GetPrice();
    string GetDescription();
    int GetRange();
}

ConcreteComponent

public class BasicTeslaModel3 : ITeslaModel3
{
    public string GetDescription()
    {
        return "Tesla Model 3 Rear-Wheel Drive";
    }

    public decimal GetPrice()
    {
        return 38990m;
    }

    public int GetRange()
    {
        return 272;
    }
}

Decorator

public abstract class TeslaDecorator(ITeslaModel3 car) : ITeslaModel3
{
    protected ITeslaModel3 _car = car;

    public virtual string GetDescription()
    {
        return _car.GetDescription();
    }

    public virtual decimal GetPrice()
    {
        return _car.GetPrice();
    }

    public virtual int GetRange()
    {
        return _car.GetRange();
    }
}

ConcreteDecorator1

public class RedPaintTeslaDecorator(ITeslaModel3 car) : TeslaDecorator(car)
{
    public override decimal GetPrice()
    {
        return base.GetPrice() + 2000;
    }

    public override string GetDescription()
    {
        return $"{base.GetDescription()}, Red Paint";
    }
}

ConcreteDecorator2

public class LongRangeTeslaDecorator(ITeslaModel3 car) : TeslaDecorator(car)
{
    public override decimal GetPrice()
    {
        return base.GetPrice() + 3500;
    }

    public override string GetDescription()
    {
        return $"{base.GetDescription()}, Long Range";
    }

    public override int GetRange()
    {
        return base.GetRange() + 91;
    }
}

ConcreteDecorator3

public class BluePaintTeslaDecorator(ITeslaModel3 car) : TeslaDecorator(car)
{
    public override decimal GetPrice()
    {
        return base.GetPrice() + 1000;
    }

    public override string GetDescription()
    {
        return $"{base.GetDescription()}, Blue Paint";
    }
}