SetUpMainPage should work with MvvmNanoViewModelBase instead

[opcodewriter]

SetUpMainPage accepts only a MvvmNanoViewModel view-model type. If you have a MvvmNanoViewModel<T> view-model, you can't use it with SetUpMainPage.

Scenario: I have a login page and registration page. After use registered successfully, I want to navigate to login page and remove the registration page from back-stack. For that I need to know in presenter whether the registration page should really be removed. So I was thinking to use an initialization parameter for the view-model which I can check in view-presenter and remove registration page from back-stack.

For this particular scenario where I need to remove page from back-stack (a logic for the view presenter), maybe a more correct approach would be to have a presentation parameter in NavigateTo, similar to how MvvmCross has it, which can be used by presenter to do some specific things.

For now, not sure which is the best workaround..

[aspnetde]

I reached this limitation, too, but I didn't have the time to update the framework (will do so later). But: SetUpMainPage() basically does this:

MainPage = new MvvmNanoNavigationPage(GetPageFor<TViewModel>());

So what you really need is a second GetPageFor() method, which accepts a navigation parameter. And here it is:

public MvvmNanoContentPage<TViewModel> GetPageFor<TViewModel, TNavigationParameter>(TNavigationParameter navigationParameter) where TViewModel : IViewModel<TNavigationParameter>
{
    var viewModel = MvvmNanoIoC.Resolve<TViewModel>() as IViewModel<TNavigationParameter>;
    viewModel.Initialize(navigationParameter);

    var page = MvvmNanoIoC
        .Resolve<IPresenter>()
        .CreateViewFor<TViewModel>() as MvvmNanoContentPage<TViewModel>;

    if (page == null)
        throw new MvvmNanoException("Could not create a MvvmNanoContentPage for View Model of type " + typeof(TViewModel) + ".");

    page.SetViewModel(viewModel);

    return page;
}

Having parameters which are directly and only accessible by the Presenter could be a considerable option, for now I am passing those parameters through the Page. So when a ViewModel is being called with a navigation paramter, I can make this available to the presenter with a public property in the Page of the View Model.

[opcodewriter]

Thanks! I think having a clear separation between parameters for presenter and for view-model would be good, otherwise the view-model get a parameter when its logic actually doesn't need one.

[aspnetde]

Agreed and looking forward to your pull request ;)