Ch3Beverage: Complete first part of the exercise

Ch3Beverage/Beverage.cs

@@ -6,6 +6,11 @@ public abstract class Beverage {
     public abstract double Cost();
 }
 
+// public static class BeveragePrintExtension {
+//     public static void Print(this Beverage value) {
+//         Console.WriteLine($"{value.Description} ${value.Cost()}");
+//     }
+// }
 /*
    The only real benefit of putting the constructor in CondimentDecorator is if you need to:
    Add validation logic (e.g., null checks) once for all decorators
@@ -18,7 +23,15 @@ public abstract class Beverage {
    but not a hard rule. Your implementation follows the Decorator pattern correctly.
  */
 
-public abstract class CondimentDecorator : Beverage;
+public abstract class CondimentDecorator(Beverage beverage) : Beverage {
+    protected Beverage Beverage { get; } = beverage;
+    /*
+     * Adding { get; } this Beverage is not a Field but a read-only Property
+     * providing a contract that child classes cannot change this value.
+     * Leaving a normal field `protected Beverage Beverage = beverage` allows
+     * child classes to freely reassign it.
+     */
+}
 
 public class Espresso : Beverage {
     public override string Description => "Espresso";
@@ -44,8 +57,21 @@ public class Decaf : Beverage {
     public override double Cost() => 1.05;
 }
 
-public class Mocha(Beverage beverage) : CondimentDecorator {
-    public override string Description => $"{beverage.Description}, Mocha";
+// Yes, this approach is really uglier because it relies aggressively
+// on inheritance (protected "invisible" variable) instead of basic explicit composition.
+// But it allows code reuse at the level of the decorator base class...
+public class Mocha(Beverage beverage) : CondimentDecorator(beverage) {
+    public override string Description => $"{Beverage.Description}, Mocha";
 
-    public override double Cost() => beverage.Cost() + 0.20;
+    public override double Cost() => Beverage.Cost() + 0.20;
+}
+
+public class Soy(Beverage beverage) : CondimentDecorator(beverage) {
+    public override string Description => $"{Beverage.Description}, Soy";
+    public override double Cost() => Beverage.Cost() + 0.15;
+}
+
+public class Whip(Beverage beverage) : CondimentDecorator(beverage) {
+    public override string Description => $"{Beverage.Description}, Whipped";
+    public override double Cost() => Beverage.Cost() + 0.10;
 }

Ch3Beverage/Program.cs

@@ -1,3 +1,24 @@
 // See https://aka.ms/new-console-template for more information
 
-Console.WriteLine("Hello, World!");
+using Ch3Beverage;
+
+
+Beverage beverage = new Espresso();
+beverage.Print();
+Beverage beverage2 = new DarkRoast();
+beverage2 = new Mocha(new Mocha(beverage2));
+beverage2 = new Whip(beverage2);
+beverage2.Print();
+Beverage beverage3 = new HouseBlend();
+beverage3 = new Soy(beverage3);
+beverage3 = new Mocha(beverage3);
+beverage3 = new Whip(beverage3);
+beverage3.Print();
+
+public static class BeveragePrintExtension {
+    // Bored, I've mode an extension method to easily print a Beverage. LOL.
+    // Because Bored, I didn't wrap this in a namespace... in real code it's necessary.
+    public static void Print(this Beverage value) {
+        Console.WriteLine($"{value.Description} ${value.Cost()}");
+    }
+}