Support NavigationService by type

[mcvasquez]

Steps to reproduce

I'm trying to update this line from MvvmCross 4.4.0 to 5.1.1:

ShowViewModel(item.ViewModelType);

Where item.ViewModelType (System.Type) contains the typeof a MvxViewModel. Ex:

typeof(MyFirstViewModel);

I'm doing this because I have a list of items with different ViewModel to navigate in a single MvxCommand.

Expected behavior

Navigate through a ViewModel by type.

Actual behavior

NavigationService does not support navigation by System.Type.

Configuration

Version: 5.1.1

Platform:

• iOS
• Android
• WPF
• UWP

[b099l3]

Hey in one of the projects I have been working on I build a menu generator that has similar functionality, e.g., passing by type. I created some extensions on the navigation service. I'll create a PR with this to see if it fixes this issue.

Edit Just realised you have done this already

[martijn00]

Hehe sorry @b099l3 it would be nice seeing some other contributions then! I don't know what sort of menu generator you made, but i would like to have some bindings for the Android NavigationLayout sometime.

[b099l3]

I was basically using reflection to create generic Navigate<TViewModel, TParameter> methods like this:

public static Task NavigateToViewModel(this IMvxNavigationService navigationService, Type viewModel, object parameter = null)
{
    try
    {
        if (parameter == null)
        {
            // Generic Method creation with reflection
            //NavigationService.Navigate<ViewModel>();
            var NavigateGenericList = typeof(MvxNavigationService).GetMethods();
            var NavigateGeneric = NavigateGenericList.Where(x =>
                                                            x.Name == "Navigate" &&
                                                            x.IsGenericMethod &&
                                                            x.GetParameters().Length == 1).FirstOrDefault();
            var NavigateGenericMethod = NavigateGeneric.MakeGenericMethod(new[] { viewModel });
            return (Task)NavigateGenericMethod.Invoke(navigationService, new object[] { null });
        }
        else
        {
            // Using reflection to generate the generic method at runtime.
            //NavigationService.Navigate<NextViewModel, MyObject>(new MyObject());
            var NavigateGenericList = typeof(MvxNavigationService).GetMethods();
            var NavigateGeneric = NavigateGenericList.Where(x =>
                                                            x.Name == "Navigate" &&
                                                            x.IsGenericMethod &&
                                                            x.GetParameters().Length == 2).FirstOrDefault();
            var NavigateGenericMethod = NavigateGeneric.MakeGenericMethod(new[] { viewModel, parameter.GetType() });
            return (Task)NavigateGenericMethod.Invoke(navigationService, new object[] { parameter, null });
        }
    }
    catch (Exception ex)
    {
        throw new MvxNavigationServiceExtensionException(viewModel, parameter, ex);
    }
}

Its quite brittle but needed to finish the project quick. I see the Navigate method signature has changed so I won't need my extension in Mvx 5.2 👍