MvvmCross Viewmodel creation issue

Question

I'm not able to instantiate the viewmodel when the viewmodel dependencies spread across different projects.

The ViewModel constructor is as follows:

public MyViewModel(IMyBusinessLogic businessLogic)
{
   ...
}


public class App : Cirrious.MvvmCross.ViewModels.MvxApplication
{
    public override void Initialize()
    {
        CreatableTypes().
            EndingWith("BusinessLogic").
            AsInterfaces().
            RegisterAsLazySingleton();
        RegisterAppStart<MyViewModel>();
    }
}

IMyBusinessLogic is in different project of the same solution. The actual implementation of this interface is in a different project.

I have added business logic interface project as a reference in viewmodel project.

Can anyone help in resolving this issue?

The Error log:

mvx:Diagnostic: 0.12 Showing ViewModel MyViewModel 'TaskHost.exe' (CoreCLR: Silverlight AppDomain): Loaded 'C:\Data\Programs{9E891FD9-C43E-4ED3-9EDC-153E29371D89}\Install\BusinessLogic.Interface.DLL'. Symbols loaded. mvx:Warning: 0.38 Problem creating viewModel of type MyViewModel - problem MvxIoCResolveException: Failed to resolve parameter for parameter myBusinessLogic of type IMyBusinessLogic when creating ViewModel.Core.MyViewModel at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.GetIoCParameterValues(Type type, ConstructorInfo firstConstructor) at Cirrious.CrossCore.IoC.MvxSimpleIoCContainer.IoCConstruct(Type type)
at Cirrious.CrossCore.Mvx.IocConstruct(Type t) at Cirrious.MvvmCross.ViewModels.MvxDefaultViewModelLocator.TryLoad(Type viewModelType, IMvxBundle parameterValues, IMvxBundle savedState, IMvxViewModel& viewModel) 'TaskHost.exe' (CoreCLR: Silverlight AppDomain): Loaded 'C:\windows\system32\en-US\mscorlib.debug.resources.dll'. Module was built without symbols.

@ Stuart: As it was mentioned in the wiki, i have override the method GetViewModelAssemblies() in the Setup.cs which exist in the platform specific UI project.

protected override Assembly[] GetViewModelAssemblies()
        {
            var list = new List<Assembly>();
            list.AddRange(base.GetViewModelAssemblies());
            list.Add(typeof(BusinessLogic.Core.MyBusinessLogic).Assembly);
            list.Add(typeof(BusinessLogic.Interface.IMyBusinessLogic).Assembly);

            return list.ToArray();
        }

But now what i have observed is the sequence of call is first App.Initialize() and then Setup.GetViewModelAssemblies(). so again i'm seeing the same issue that it is not able to find the required type from IoC to craete the viewmodel. Any suggestion on this?

I did some more analysis. Currently what i have observed is that, the MvxApplication: CreatableTypes() method is looking up only the current Dll, and not the other Dll which were got loaded. And since my interface and actual implementation of the interface are in different dlls, this is not able to lookup in those dlls, and hence Business logic classes are not getting registered. Is there any way i can make the MvxApplication: CreatableTypes() method to lookup in all the loaded Dlls? — tsr
I'm on mobile at the moment... But this is in the wiki somewhere - look for view model assemblies in setup — Stuart
@Stuart : tried to override GetViewModelAssemblies (as shown in the above question). Still getting the same issue. Anything i'm missing here? — tsr

Stuart Stuart · Accepted Answer · 2014-05-01T08:03:34

For looking up ViewModels in multiple assemblies, you can use https://github.com/MvvmCross/MvvmCross/wiki/Customising-using-App-and-Setup#providing-additional-view-and-viewmodel-assemblies

protected override Assembly[] GetViewModelAssemblies()
{
    var list = new List<Assembly>();
    list.AddRange(base.GetViewModelAssemblies());
    list.Add(typeof(SomeTypeFromAdditionalViewModelAssembly1).Assembly);
    list.Add(typeof(SomeTypeFromAdditionalViewModelAssembly2).Assembly);
    list.Add(typeof(SomeTypeFromAdditionalViewModelAssembly3).Assembly);
    // ...
    return list.ToArray();
}

For IoC registering services from different assemblies, there's an Assembly extension method available - see https://github.com/MvvmCross/MvvmCross/wiki/Service-Location-and-Inversion-of-Control#bulk-registration-by-convention

If you're looking to understand how IoC works in MvvmCross, then https://github.com/MvvmCross/MvvmCross/wiki/Service-Location-and-Inversion-of-Control is a good starting point <- recommended reading.

you can you can also, of course, use the same type of registration logic on assemblies other than Core - e.g.:
   typeof(Reusable.Helpers.MyHelper).Assembly.CreatableTypes()
       .EndingWith("Helper")
       .AsInterfaces()
       .RegisterAsDynamic();

MvvmCross Viewmodel creation issue

1 Answers