CODEWITHSUNDEEP
xamarin.formsreactive-programmingmaster-detailreactiveui
M Yil
M Yil

Reputation: 967

Xamarin Forms / ReactiveUI - Using ReactiveUI for masterdetail page shows that viewmodel is null

I have a xamarin forms application that is based on ReactiveUI. The viewmodels inherit from ReactiveObject and the codebehind the xaml of the pages , they inherit/are based on from ReactiveContentPage, in case of the masterdetailpage it inherits from the ReactiveMasterDetailPage. The contentpages/masterdetailpage it self are based on ReactiveContent.

What I want to achieve is the following: Get views/xamlpages by giving a viewmodel type. I have the following code for that. But it gives a null at _viewLocator.Resolve...

        public async Task<TViewModel> PushViewModelAsync<TViewModel>(bool animated) where TViewModel : class
    {
        var viewModel = DependencyInjectionService.Get<TViewModel>();
        var view = _viewLocator.ResolveView(viewModel);

        if (view is Page page)
        {
            view.ViewModel = viewModel;

            await Application.Current.MainPage.Navigation.PushAsync(page, animated);
            return viewModel;
        }
        else
        {
            throw new ArgumentException($"resolved view for {typeof(TViewModel)} is not a page.");
        }
    }

The problem is that this works for normal contentpages but it doesnt work for my MasterDetailPage, how is that possible?

      <?xml version="1.0" encoding="utf-8" ?>
       <rxui:ReactiveMasterDetailPage xmlns="http://xamarin.com/schemas/2014/forms"
           xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
           xmlns:d="http://xamarin.com/schemas/2014/forms/design"
           xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             mc:Ignorable="d"
         xmlns:vm="clr-namespace:DriverApp.ViewModels"
         x:TypeArguments="vm:MainViewModel"      
         xmlns:rxui="clr-namespace:ReactiveUI.XamForms;assembly=ReactiveUI.XamForms"
         xmlns:local="clr-namespace:DriverApp.Views; assembly=MasterDetailPageNavigation"
         x:Class="DriverApp.Views.MainPage"
         Title="Personal Organiser">

<MasterDetailPage.Master>
    <local:MasterPage x:Name="masterPage" />
</MasterDetailPage.Master>

<MasterDetailPage.Detail>
    <NavigationPage>
        <x:Arguments>
            <local:PlanningPage/>
        </x:Arguments>
    </NavigationPage>
</MasterDetailPage.Detail>

The viewmodel:

public class MainViewModel : ReactiveObject, IActivatableViewModel
{

}

I inject it like this:

        services.AddTransient<IViewFor<MainViewModel>, MainPage>();

Upvotes: 0

Views: 227

Answers (1)

Rodney Littles
Rodney Littles

Reputation: 564

var viewModel = DependencyInjectionService.Get<TViewModel>();
var view = _viewLocator.ResolveView(viewModel);

Based on the code provided I would expect the value you are passing into the _viewLocator.ResolveView to be null. You showed the code where you are registering the IViewFor but I don't see any code registering the ViewModel itself.

Registering IViewFor<Foo>, Foo doesn't register the view model. It tells the type system that a given ViewModel will resolve a specific page.

Also, it seems like you are using a different container than the one provided by ReactiveUI. Which is okay, but you have to make sure all your dependencies are registered correctly in the container you plan to resolve dependencies from.

Lastly. You say it gives a null, but you don't say if the ViewModel you are passing is null or the object you are using to resolve is null.

Either way, I think this is an issue of having the dependencies registered in the correct place, based on the information provided.

Upvotes: 0

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