6.1.3 Creating Chains of Dependency

chap6_essential_tools_for_mvc/NinjectDemo/Product.cs

@@ -18,9 +18,16 @@ namespace NinjectDemo
 
     public class LinqValueCalculator : IValueCalculator
     {
+        private IDiscountHelper discounter;
+
+        public LinqValueCalculator(IDiscountHelper discountParam)
+        {
+            discounter = discountParam;
+        }
+
         public decimal ValueProducts(params Product[] products)
         {
-            return products.Sum(p => p.Price);
+            return discounter.ApplyDiscount(products.Sum(p => p.Price));
         }
     }
 }

chap6_essential_tools_for_mvc/NinjectDemo/Program.cs

@@ -14,6 +14,7 @@ namespace NinjectDemo
         {
             IKernel ninjectKernel = new StandardKernel();
             ninjectKernel.Bind<IValueCalculator>().To<LinqValueCalculator>();
+            ninjectKernel.Bind<IDiscountHelper>().To<DefaultDiscountHelper>();
             
             // get the interface implementation
             IValueCalculator calcImp1 = ninjectKernel.Get<IValueCalculator>();
@@ -23,4 +24,17 @@ namespace NinjectDemo
             Console.WriteLine("Total: {0:c}", cart.CalculateStockValue());
         }
     }
+
+    public interface IDiscountHelper
+    {
+        decimal ApplyDiscount(decimal totalParam);
+    }
+
+    public class DefaultDiscountHelper : IDiscountHelper
+    {
+        public decimal ApplyDiscount(decimal totalParam)
+        {
+            return (totalParam - (10m / 100m * totalParam));
+        }
+    }
 }