PopupService

[bijington]

Description of Change

Linked Issues

• Fixes [Proposal] PopupService #981

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: https://github.com/MicrosoftDocs/CommunityToolkit/pull/XYZ

Additional information

[MDale-RAC]

Any updates on this?

[bijington]

Any updates on this?

No I haven't been able to determine what the best option is for IArgumentsReceiver - whether we want a different name or better abstraction. Any input is welcome :)

[bijington]

As an alternative to requiring an interface when presenting the popup for the view model to receive data we could try something like this:

public Task<object?> ShowPopupAsync<TViewModel>(Action<TViewModel> onPresenting) where TViewModel : INotifyPropertyChanged
{
    ArgumentNullException.ThrowIfNull(onPresenting);

    var popup = GetPopup(typeof(TViewModel));

    var viewModel = GetViewModel<TViewModel>();

    popup.BindingContext = viewModel;

    onPresenting.Invoke(viewModel);

    return CurrentPage.ShowPopupAsync(popup);
}

The onPresenting action would be invoked once the view model is created and assigned to the popup BindingContext, just before the popup is presented.

It could then be used as follows:

public class MyViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler? PropertyChanged;

    public void LoadData(int id)
    {
    }
}

void Show()
{
    ShowPopupAsync<MyViewModel>(onPresenting: viewModel => viewModel.LoadData(123));
}

What do people think? Is it clean or a bit yucky?

[VladislavAntonyuk]

As an alternative to requiring an interface when presenting the popup for the view model to receive data we could try something like this:

public Task<object?> ShowPopupAsync<TViewModel>(Action<TViewModel> onPresenting) where TViewModel : INotifyPropertyChanged
{
    ArgumentNullException.ThrowIfNull(onPresenting);

    var popup = GetPopup(typeof(TViewModel));

    var viewModel = GetViewModel<TViewModel>();

    popup.BindingContext = viewModel;

    onPresenting.Invoke(viewModel);

    return CurrentPage.ShowPopupAsync(popup);
}

The onPresenting action would be invoked once the view model is created and assigned to the popup BindingContext, just before the popup is presented.

It could then be used as follows:

public class MyViewModel : INotifyPropertyChanged
{
    public event PropertyChangedEventHandler? PropertyChanged;

    public void LoadData(int id)
    {
    }
}

void Show()
{
    ShowPopupAsync<MyViewModel>(onPresenting: viewModel => viewModel.LoadData(123));
}

What do people think? Is it clean or a bit yucky?

I like it, but make it Func<ViewModel, Task>

[brminnick]

Thanks Shaun!! I'm excited to see PopupService finally become a reality!!

I'm going to merge this right away so that we can squeeze it into this week's release.

Could you prioritize getting the PopupService docs done before Monday so that PopupService doesn't go too long without proper documentation?

FYI - I made a small tweak, removing PopupService's functionality that automatically assigned BindingContexts. I renamed the method to ValidateBindingContext (below) to ensure that the user has properly assigned the Popup View's BindingContext. However, I think it's out-of-scope for the PopupService to automatically assign it for them.

For example, .NET MAUI doesn't automatically assign a ContentPage's BindingContext when a user passes it into IServiceCollection.

I'm happy to circle back to this discussion in the future if we get requests from the community. But I agree that PopupService should be opinionated, and it should require the correct BindingContext. And us throwing an InvalidOperationException is enough to inform the dev of the requirement, in lieu of doing it for them under the hood (which they may not expect/want).

static void ValidateBindingContext<TViewModel>(Popup popup, out TViewModel bindingContext)
{
 if (popup.BindingContext is not TViewModel viewModel)
 {
 	throw new InvalidOperationException($"Unexpected type has been assigned to the BindingContext of {popup.GetType().FullName}. Expected type {typeof(TViewModel).FullName} but was {popup.BindingContext?.GetType().FullName?? "null"}");
 }

 bindingContext = viewModel;
}