Immutable IoC container for Prism.Autofac.Forms - resolution to issue # 969

Source/Xamarin/Prism.Autofac.Forms.Tests/Mocks/PrismApplicationMock.cs

@@ -5,17 +5,15 @@
 using Prism.Modularity;
 using Prism.Navigation;
 using Xamarin.Forms;
-using Autofac;
 
 namespace Prism.Autofac.Forms.Tests.Mocks
 {
     public class PrismApplicationMock : PrismApplication
     {
         public PrismApplicationMock()
-        {
-        }
+        { }
 
-        public PrismApplicationMock(Page startPage) : this()
+        public PrismApplicationMock(Page startPage)
         {
             Current.MainPage = startPage;
         }
@@ -41,28 +39,26 @@ protected override void ConfigureModuleCatalog()
 
         protected override void RegisterTypes()
         {
-            var builder = new ContainerBuilder();
-
-            builder.RegisterType<ServiceMock>().As<IServiceMock>();
-            builder.RegisterType<AutowireViewModel>();
-            builder.RegisterType<ViewModelAMock>();
-            builder.Register(ctx => new ViewModelBMock()).Named<ViewModelBMock>(ViewModelBMock.Key);
-            builder.RegisterType<ConstructorArgumentViewModel>();
-            builder.RegisterType<ModuleMock>().SingleInstance();
+            FormsDependencyService.Register<IDependencyServiceMock>(new DependencyServiceMock());
 
-            builder.Update(Container);
+            Container.RegisterType<ServiceMock>().As<IServiceMock>();
+            Container.RegisterType<AutowireViewModel>();
+            Container.RegisterType<ViewModelAMock>();
+            Container.Register(ctx => new ViewModelBMock()).Named<ViewModelBMock>(ViewModelBMock.Key);
+            Container.RegisterType<ConstructorArgumentViewModel>();
+            Container.RegisterType<ModuleMock>().SingleInstance();
+            Container.Register(ctx => FormsDependencyService.Get<IDependencyServiceMock>())
+                .As<IDependencyServiceMock>();
 
             Container.RegisterTypeForNavigation<ViewMock>("view");
             Container.RegisterTypeForNavigation<ViewAMock, ViewModelAMock>();
             Container.RegisterTypeForNavigation<AutowireView, AutowireViewModel>();
             Container.RegisterTypeForNavigation<ConstructorArgumentView, ConstructorArgumentViewModel>();
-
-            FormsDependencyService.Register<IDependencyServiceMock>(new DependencyServiceMock());
         }
 
         public INavigationService CreateNavigationServiceForPage()
         {
             return CreateNavigationService();
         }
     }
-}
+}

Source/Xamarin/Prism.Autofac.Forms.Tests/PrismApplicationFixture.cs

@@ -1,5 +1,5 @@
 using System;
-using System.Reflection;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 using Prism.Common;
 using Prism.Autofac.Forms.Tests.Mocks;
@@ -12,7 +12,6 @@
 using Xamarin.Forms;
 using Xunit;
 using Autofac;
-using Autofac.Core.Registration;
 using Prism.DI.Forms.Tests;
 #if TEST
 using Application = Prism.FormsApplication;
@@ -62,11 +61,15 @@ public void ResolveConcreteTypeNotRegisteredWithContainer()
         public void ResolveTypeRegisteredWithDependencyService()
         {
             var app = new PrismApplicationMock();
-            //TODO: Autofac needs to be updated to support resolving unknown interfaces by using the DependencyService
-            Assert.Throws<ComponentNotRegisteredException>(() => app.Container.Resolve<IDependencyServiceMock>());
-            //var service = app.Container.Resolve<IDependencyServiceMock>();
-            //Assert.NotNull(service);
-            //Assert.IsType<DependencyServiceMock>(service);
+
+            //Was: Autofac needs to be updated to support resolving unknown interfaces by using the DependencyService
+            //Assert.Throws<ComponentNotRegisteredException>(() => app.Container.Resolve<IDependencyServiceMock>());
+
+            //  Update 2017-04-03: Probably don't need this support, since use of DependencyService is being deprecated.
+            //  So added "support" for it by secondarily registering the service directly in the Autofac container.
+            var service = app.Container.Resolve<IDependencyServiceMock>();
+            Assert.NotNull(service);
+            Assert.IsType<DependencyServiceMock>(service);
         }
 
         [Fact]
@@ -131,5 +134,24 @@ private static INavigationService ResolveAndSetRootPage(PrismApplicationMock app
             ((IPageAware)navigationService).Page = new ContentPage();
             return navigationService;
         }
+
+        [Fact]
+        public void Container_IsImmutableAfterBuild()
+        {
+            //Arrange
+            var app = new PrismApplicationMock();
+
+            //Act
+            //Referencing the Container's ComponentRegistry causes the Container to be built
+            //  and no further type registration should be possible.
+            var componentRegistry = app.Container.ComponentRegistry;
+
+            //Assert
+            Assert.True(app.Container.IsContainerBuilt);
+            Assert.Throws<InvalidOperationException>(() => app.Container.Register(ctx => new List<string>())
+                .As<IList<string>>());
+            //But type resolution will work properly
+            Assert.NotNull(app.Container.Resolve<ViewModelAMock>());
+        }
     }
 }

Source/Xamarin/Prism.Autofac.Forms/AutofacExtensions.cs

@@ -65,7 +65,8 @@ public static IContainer RegisterTypeForNavigation<TView, TViewModel>(this ICont
         /// <param name="otherView">Other Platform Specific View Type</param>
         /// <param name="windowsView">Windows Specific View Type</param>
         /// <param name="winPhoneView">Windows Phone Specific View Type</param>
-        /// <returns><see cref="IUnityContainer"/></returns>
+        /// <returns><see cref="IContainer"/></returns>
+        // ReSharper disable once InconsistentNaming
         public static IContainer RegisterTypeForNavigationOnPlatform<TView, TViewModel>(this IContainer container, string name = null, Type androidView = null, Type iOSView = null, Type otherView = null, Type windowsView = null, Type winPhoneView = null)
             where TView : Page
             where TViewModel : class
@@ -109,7 +110,7 @@ public static IContainer RegisterTypeForNavigationOnPlatform<TView, TViewModel>(
         /// <param name="desktopView">Desktop Specific View Type</param>
         /// <param name="tabletView">Tablet Specific View Type</param>
         /// <param name="phoneView">Phone Specific View Type</param>
-        /// <returns><see cref="IUnityContainer"/></returns>
+        /// <returns><see cref="IContainer"/></returns>
         public static IContainer RegisterTypeForNavigationOnIdiom<TView, TViewModel>(this IContainer container, string name = null, Type desktopView = null, Type tabletView = null, Type phoneView = null)
             where TView : Page
             where TViewModel : class
@@ -151,6 +152,7 @@ private static IContainer RegisterTypeForNavigationWithViewModel<TViewModel>(thi
         /// after the container is already created.
         /// Uses a new ContainerBuilder instance to update the Container.
         /// </summary>
+        /// <param name="container">The container to register type with</param>
         /// <param name="type">The type to register.</param>
         /// <param name="name">The name you will use to resolve the component in future.</param>
         /// <param name="registerAsSingleton">Registers the type as a singleton.</param>
@@ -162,16 +164,27 @@ private static void RegisterTypeIfMissing(IContainer container, Type type, strin
             if (name == null)
                 throw new ArgumentNullException(nameof(name));
 
-            if (!container.IsRegistered(type))
+            if (container is IAutofacContainer afContainer)
             {
-                var containerUpdater = new ContainerBuilder();
-
-                if (registerAsSingleton)
-                    containerUpdater.RegisterType(type).Named<Page>(name).SingleInstance();
-                else
-                    containerUpdater.RegisterType(type).Named<Page>(name);
-
-                containerUpdater.Update(container);
+                //TODO: In the future, the use of IsTypeRegistered() should be eliminated and these should be done as conditional 
+                //  registrations instead: http://docs.autofac.org/en/latest/register/registration.html#conditional-registration
+                //  But conditional registrations are not available until Autofac 4.4.0, and we are only requiring 3.5.2 at this time
+
+                if (!afContainer.IsTypeRegistered(type))
+                {
+                    if (registerAsSingleton)
+                    {
+                        afContainer.RegisterType(type).Named<Page>(name).SingleInstance();
+                        //With conditional registration in Autofac 4.4.0 and higher, it will look something like this:
+                        //afContainer.Builder.RegisterType(type).Named<Page>(name).SingleInstance().IfNotRegistered(type);
+                    }
+                    else
+                    {
+                        afContainer.RegisterType(type).Named<Page>(name);
+                        //With conditional registration in Autofac 4.4.0 and higher, it will look something like this:
+                        //afContainer.Builder.RegisterType(type).Named<Page>(name).IfNotRegistered(type);
+                    }
+                }
             }
         }
     }

Source/Xamarin/Prism.Autofac.Forms/IPlatformInitializer.cs

@@ -1,8 +1,6 @@
-using Autofac;
-
-namespace Prism.Autofac.Forms
+namespace Prism.Autofac.Forms
 {
-    public interface IPlatformInitializer : IPlatformInitializer<IContainer>
+    public interface IPlatformInitializer : IPlatformInitializer<IAutofacContainer>
     {
     }
 }