IViewResolver
As we have already wrote when we spoke about Runtime Conventions Radical utilizes by default a view first approach, that even if is completely replaceable with a ViewModel first approach, must be understood.
The main and only entry point used to resolve views is
IViewResolver
interface whose role is to resolve a view instance given a view type:IViewResolver service; //injected by the IoC engine
var viewUsingGenerics = service.GetView<SampleView>();
var viewUsingType = service.GetView( typeof( SampleView ) );
At runtime when the
GetView
method is called the default built-in view resolver does the following things:- 1.goes to the IoC container and resolves an instance of the requested view type;
- 2.if the view already has a
DataContext
it assumes that the view is a singleton and has been already resolved once and immediately returns the resolved view; - 3.Otherwise, using the conventions:
- 4.Using the
ResolveViewModelType
convention determines the type of the associated ViewModel; - 5.Resolves, via the container, the ViewModel;
- 6.Set the relation View – ViewModel;
- 7.Set the ViewModel as the DataContext of the View;
- 8.Attaches to the View the required behaviors;
- 9.Exposes services registered to be exposed as resources in the View
- 10.Returns the view to the caller;
The typical usage of the view resolver in the application is to open/show another view, the easiest way is to declare a dependency on the resolver in our component:
class SampleViewModel
{
readonly IViewResolver service;
public SampleViewModel( IViewResolver service )
{
this.service = service;
}
public void ShowAView()
{
var myView = this.service.GetView<MyView>();
myView.Show();
}
}
We are using the simplest possible approach in order to keep the sample complexity really low.
- In the above sample we are violating the MVVM pattern because we are dealing with a view within the ViewModel, in the chapter related to the MessageBroker we’ll see how to avoid this mix.
- A view does not require a view model to work properly, the
IViewResolver
can resolve views that don't have view models;
Last modified 1yr ago