MVUX - How to refresh a ListFeed

[mcNets]

Given a model like this, and having the Machines list bound to a FeedView, how can I refresh the list every time a filter flag changes?

namespace OsmoManager.ViewModels;

internal partial record MachineBoardModel(MachinesService MachinesService)
{
    // filter flags
    public IState<bool> Unassigned => State.Value(this, () => MachinesService.Unassigned);
    public IState<bool> Running => State.Value(this, () => MachinesService.Running);
    public IState<bool> Stopped => State.Value(this, () => MachinesService.Stopped);
    public IState<bool> OutOfService => State.Value(this, () => MachinesService.OutOfService);

    public IListFeed<MachinesListItem> Machines => ListFeed.Async(MachinesService.GetMachinesListAsync);

    public async ValueTask RefreshMachinesCommand(CancellationToken ct)
    {
        MachinesService.Unassigned = await Unassigned;
        MachinesService.Running = await Running;
        MachinesService.Stopped = await Stopped;
        MachinesService.OutOfService = await OutOfService;

        // refresh the list by calling MachinesService.GetMachinesListAsync ???
    }
}

internal class MachinesService
{
    public bool Unassigned { get; set; } = true;
    public bool Running { get; set; } = true;
    public bool Stopped { get; set; } = true;
    public bool OutOfService { get; set; } = true;

    private IImmutableList<MachinesListItem> _machines = ImmutableList<MachinesListItem>.Empty;

    public async ValueTask<IImmutableList<MachinesListItem>> GetMachinesListAsync(CancellationToken ct)
    {
        _machines = await GetFakeMachinesListAsync(ct);

        int states = 0;
        if (Unassigned) states |= (int)MachineStates.Unassigned;
        if (Running) states |= (int)MachineStates.Running;
        if (Stopped) states |= (int)MachineStates.Stopped;
        if (OutOfService) states |= (int)MachineStates.OutOfService;

        return _machines.Where(x => ((int)x.State & states) > 0).ToImmutableList();
    }
}

[dr1rrb]

My suggestion here would be to change the architecture into a more declarative/reactive approach (I'm adding doc about this here #2361)

To apply it to your case:

namespace OsmoManager.ViewModels;

internal partial record MachineBoardModel(MachinesService MachinesService)
{
    public IState<MarchineCriteria> Criteria => State.Value(this, () => new MarchineCriteria());
    public IListFeed<MachinesListItem> Machines => Criteria.Select(MachinesService.GetMachinesListAsync).AsListFeed();
}

internal partial record MarchineCriteria(bool Unassigned, bool Running, bool Stopped, out OutOfService);

internal class MachinesService
{
    private IImmutableList<MachinesListItem> _machines = ImmutableList<MachinesListItem>.Empty;

    public async ValueTask<IImmutableList<MachinesListItem>> GetMachinesListAsync(MarchineCriteria criteria, CancellationToken ct)
    {
        _machines = await GetFakeMachinesListAsync(ct);

        int states = 0;
        if (criteria.Unassigned) states |= (int)MachineStates.Unassigned;
        if (criteria.Running) states |= (int)MachineStates.Running;
        if (criteria.Stopped) states |= (int)MachineStates.Stopped;
        if (criteria.OutOfService) states |= (int)MachineStates.OutOfService;

        return _machines.Where(x => ((int)x.State & states) > 0).ToImmutableList();
    }
}

And you can then edit the Criteria from the view by simply binding 2-way to Criteria.Unassigned, Criteria.Running, etc. Each time a criteria is changed, a request will be sent and the Machines will be updated.

And if you still want to let the user to refresh the list, you can also use the Refresh command exposed by the FeedView. It can be used directly within the ListView (e.g. pull-to-refresh) or externally (e.g. in a command bar)

[francoistanguay]

I think you need to use .Select(...).AsListFeed()

https://platform.uno/docs/articles/external/uno.extensions/doc/Reference/Reactive/listfeed.html#aslistfeed

[mcNets]

That's what I am using, have a look at David example:

internal partial record MachineBoardModel(MachinesService MachinesService)
{
    public IState<MarchineCriteria> Criteria => State.Value(this, () => new MarchineCriteria());
    public IListFeed<MachinesListItem> Machines => Criteria.Select(MachinesService.GetMachinesListAsync).AsListFeed();
}

[francoistanguay]

Sorry, what is the question? Is the syntax above compiling and working or not? Error?

[mcNets]

Sorry @francoistanguay

The error I'm getting here:

public IListFeed<MachinesListItem> Machines => Criteria.Select(MachinesService.GetMachinesListAsync).AsListFeed();

CS0411 The type arguments for method 'Feed.Select<TSource, TResult>(IFeed, Func<TSource, TResult>)' cannot be inferred from the usage. Try specifying the type arguments explicitly.

[mcNets]

I'm able to get the list in this way:

public IListFeed<MachinesListItem> Machines
{
    get
    {
        var feed = Feed.Async(
            async ct =>
            {
                var criteria = await Criteria;
                var machines = await MachinesService.GetMachinesListAsync(criteria, ct);
                return machines;
            });
        return feed.AsListFeed();
        //return Criteria.Select(MachinesService.GetMachinesListAsync).AsListFeed();
    }
}

[mcNets]

@francoistanguay @dr1rrb Solved, Select must be SelectAsync

[dr1rrb]

Oh sorry indeed.