Handling MvxViewModel::Close when using custom view presenters

Question

I am using a custom view presenter in my Windows Store app.

I show a SettingsFlyout and in its SettingsViewModel view-model I have a command bound to a button on the flyout which needs to hide the flyout (SettingsFlyout::Hide()).

For this, I have different options:

• in the SettingsFlyout, I can handle the button click

• in the ICommand in the view-model, send a message from view-model to view

• in the ICommand in the view-model, call Close(this).

  I was trying to implement last one, using Close(this) in the view-model.

  For this, in the custom view presenter I was thinking to handle ChangePresentation(MvxPresentationHint hint) or Close(IMvxViewModel viewModel).

  But I don't see how to get the view instance corresponding to the view-model instance.

  In my case I have the SettingsViewModel instance and I need to get the instance of the displayed SettingsFlyout.

  Is there a way?

Answer 1

This is a custom presentation/navigation, so this is left open to the individual app to implement.

Some possible ideas are:

• the Presenter could keep a list of shown Views (and then get their ViewModels by inspecting their ViewModel / DataContext property) - if doing this, be careful to remove each View from this list when they are closed otherwise this could cause horrible memory leaks.
• the SettingsFlyout class could itself just have a Current static member - or could call a singleton service which stores the Current (if needed this could be archicted into a more general solution - beyond just the SettingsFlyout)
• the Presenter could inspect and search the VisualTree for the appropriate View to close
• the Closed mechanism could be a custom event or property fired from your SettingsFlyoutViewModel to your SettingsFlyoutView - instead of using a NavigationHint.