From 592d74f9d8c1dadf71ba8805998ec1c7302f924f Mon Sep 17 00:00:00 2001
From: "Matthew D. Groves" <webmaster@mgroves.com>
Date: Sun, 6 Mar 2011 13:46:04 -0500
Subject: [PATCH] refactored ioc/service locator to hopefully improve
 clarity/readability

---
 MonoStockPortfolio/Framework/IoCAttribute.cs  | 30 +++++++++++++------
 .../Framework/ServiceLocator.cs               |  3 ++
 .../Presenters/MainPresenter.cs               |  1 -
 3 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/MonoStockPortfolio/Framework/IoCAttribute.cs b/MonoStockPortfolio/Framework/IoCAttribute.cs
index 0e15824..9d810df 100644
--- a/MonoStockPortfolio/Framework/IoCAttribute.cs
+++ b/MonoStockPortfolio/Framework/IoCAttribute.cs
@@ -1,3 +1,4 @@
+using System;
 using Android.Content;
 using PostSharp.Aspects;
 
@@ -7,17 +8,16 @@ namespace MonoStockPortfolio.Framework
     {
         public sealed override void OnGetValue(LocationInterceptionArgs args)
         {
-            args.ProceedGetValue(); 
-            if (args.Value == null)
+            args.ProceedGetValue();
+            if (args.Value == null)     // lazy loading
             {
-                if (ServiceLocator.Context == null)
-                {
-                    var activityContext = (Context) args.Instance;
-                    ServiceLocator.Context = activityContext.ApplicationContext.ApplicationContext;
-                }
+                var context = args.Instance as Context;
+                if(context == null) throw new Exception("The IoC Aspect can only be used on a field within an Activity (or Context) object");
 
-                var locationType = args.Location.LocationType;
-                var instantiation = ServiceLocator.Get(locationType);
+                ResolveContextDependency((Context)args.Instance);
+
+                var dependencyType = args.Location.LocationType;
+                var instantiation = ServiceLocator.Get(dependencyType);
 
                 if (instantiation != null)
                 {
@@ -26,5 +26,17 @@ namespace MonoStockPortfolio.Framework
                 args.ProceedGetValue();
             }
         }
+
+        private static void ResolveContextDependency(Context contextObject)
+        {
+            if (ServiceLocator.Context == null)
+            {
+                // note the double ApplicationContext
+                // is because the context's reference could get garbage collected while the app is still goin
+                // for whatever reason, but it's reference's reference is long-running
+                // and since this context dependency is mainly used for Sqlite, that's the most ideal one
+                ServiceLocator.Context = contextObject.ApplicationContext.ApplicationContext;
+            }
+        }
     }
 }
\ No newline at end of file
diff --git a/MonoStockPortfolio/Framework/ServiceLocator.cs b/MonoStockPortfolio/Framework/ServiceLocator.cs
index 9b51220..5aa1990 100644
--- a/MonoStockPortfolio/Framework/ServiceLocator.cs
+++ b/MonoStockPortfolio/Framework/ServiceLocator.cs
@@ -14,7 +14,10 @@ namespace MonoStockPortfolio.Framework
 
         static ServiceLocator()
         {
+            // presenters
             IttyBittyIoC.Register<IMainPresenter>(() => new MainPresenter(new AndroidSqlitePortfolioRepository(Context)));
+
+            // services/repositories
             IttyBittyIoC.Register<IStockDataProvider>(() => new YahooStockDataProvider());
             IttyBittyIoC.Register<IPortfolioService>(() => new PortfolioService(new AndroidSqlitePortfolioRepository(Context), new YahooStockDataProvider()));
             IttyBittyIoC.Register<IPortfolioRepository>(() => new AndroidSqlitePortfolioRepository(Context));
diff --git a/MonoStockPortfolio/Presenters/MainPresenter.cs b/MonoStockPortfolio/Presenters/MainPresenter.cs
index 4f220ab..1ffb620 100644
--- a/MonoStockPortfolio/Presenters/MainPresenter.cs
+++ b/MonoStockPortfolio/Presenters/MainPresenter.cs
@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using Android.Util;
 using MonoStockPortfolio.Core.PortfolioRepositories;
 using MonoStockPortfolio.Entities;
 using System.Linq;