design-patterns-in-csharp/Structural/Decorator/Program.cs at main · MartinMikes/design-patterns-in-csharp · GitHub

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using System;

namespace Decorator;

// Component interface
public interface ICoffee
{
    string GetDescription();
    double GetCost();
}

// Concrete Component
public class SimpleCoffee : ICoffee
{
    public string GetDescription()
    {
        return "Simple Coffee";
    }

    public double GetCost()
    {
        return 2.00;
    }
}

// Base Decorator
public abstract class CoffeeDecorator(ICoffee coffee) : ICoffee
{
    // Using C# 14 field keyword with required modifier
    protected ICoffee Coffee
    {
        get;
        init => field = value ?? throw new ArgumentNullException(nameof(value));
    } = coffee;

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

    public virtual double GetCost()
    {
        return Coffee.GetCost();
    }
}

// Concrete Decorators
public class MilkDecorator : CoffeeDecorator
{
    public MilkDecorator(ICoffee coffee) : base(coffee) { }

    public override string GetDescription()
    {
        return Coffee.GetDescription() + ", Milk";
    }

    public override double GetCost()
    {
        return Coffee.GetCost() + 0.50;
    }
}

public class SugarDecorator : CoffeeDecorator
{
    public SugarDecorator(ICoffee coffee) : base(coffee) { }

    public override string GetDescription()
    {
        return Coffee.GetDescription() + ", Sugar";
    }

    public override double GetCost()
    {
        return Coffee.GetCost() + 0.25;
    }
}

public class WhipDecorator : CoffeeDecorator
{
    public WhipDecorator(ICoffee coffee) : base(coffee) { }

    public override string GetDescription()
    {
        return Coffee.GetDescription() + ", Whipped Cream";
    }

    public override double GetCost()
    {
        return Coffee.GetCost() + 0.75;
    }
}

class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("=== Decorator Pattern Demo ===");
        Console.WriteLine();

        // Simple coffee
        ICoffee coffee = new SimpleCoffee();
        Console.WriteLine($"{coffee.GetDescription()} - ${coffee.GetCost()}");

        // Coffee with milk
        coffee = new MilkDecorator(new SimpleCoffee());
        Console.WriteLine($"{coffee.GetDescription()} - ${coffee.GetCost()}");

        // Coffee with milk and sugar
        coffee = new SugarDecorator(new MilkDecorator(new SimpleCoffee()));
        Console.WriteLine($"{coffee.GetDescription()} - ${coffee.GetCost()}");

        // Coffee with everything
        coffee = new WhipDecorator(
            new SugarDecorator(
                new MilkDecorator(new SimpleCoffee())
            )
        );
        Console.WriteLine($"{coffee.GetDescription()} - ${coffee.GetCost()}");

        Console.WriteLine();
        Console.WriteLine("Press any key to exit...");
        Console.ReadKey();
    }
}