How does ReactiveTableViewSource work?

问题

In our app we use ReactiveUI to follow the MVVM pattern. In one view we want to show a UITableView. Data are usually passed to a UITableView.Source but with ReactiveUI we use ReactiveTableViewSource<TSource>.

What I don't understand is how I can bind my data that I got in my view model in a ReactiveList to the ReactiveTableViewSource.

What we now have is that we create a table inside a UIView like this:

Table = new UITableView(UIScreen.MainScreen.Bounds);
Table.Source = new TableSource(Table, MyReactiveList, (NSString) CellIdentifier, _cellHeight, cell => Debug.WriteLine(cell));

Btw: What is the cell action used for?

Furthermore we have a Table source class that looks like this:

internal sealed class TableSource : ReactiveTableViewSource<MyListObject>
{
  public TableSource(UITableView tableView, IReactiveNotifyCollectionChanged<MyListObject> collection, NSString cellKey, float sizeHint, Action<UITableViewCell> initializeCellAction = null) : base(tableView, collection, cellKey, sizeHint, initializeCellAction)

In my view model I have a service that is updating my ReactiveList. It looks like this:

public sealed class MyService : ReactiveObject, IMyService
{
  public IReactiveList<MyListObject> MyReactiveList { get; }

  public async Task UpdateMyReactiveListAsync() {//...}

Where do I bind the table source to the ReactiveList? Where do I subscribe for events? Is there any documentation or example code I might have missed?

回答1:

Working with ReactiveTableViewSource is quite easy:

Just connect the List with your UITableView

var tableView = new UITableView ();

// Bind the List agains the table view
// SampleObject is our model and SampleCell the cell
ViewModel.WhenAnyValue (vm => vm.Items).BindTo<SampleObject, SampleCell> (tableView, 46, cell => cell.Initialize());

Then create a custom cell where you bind the model data against the cell.

public class SampleCell : ReactiveTableViewCell, IViewFor<SampleObject>
{
    public SampleCell () : base() { }
    public SampleCell (IntPtr handle) : base(handle) { }

    private SampleObject _viewModel;
    public SampleObject ViewModel
    {
        get { return _viewModel; }
        set { this.RaiseAndSetIfChanged (ref _viewModel, value); }
    }

    object IViewFor.ViewModel
    {
        get { return ViewModel; }
        set { ViewModel = value as SampleObject; }
    }

    public void Initialize()
    {
        this.WhenAnyValue (v => v.ViewModel.Name).BindTo (
            this,
            v => v.TextLabel.Text);
    }
}

A compelling example you can find here: https://github.com/reicheltp/ReactiveTableViewSource-Sample

Update 2016/03/09: Better do binding in a separated Initialize method to prevent multiple calls.

If you have more questions you can ask me on twitter: @reicheltp

回答2:

May be you miss this https://github.com/reactiveui/ReactiveUI/blob/275eca3dc2e5fc93bddb137e60be32885f788688/docs/basics/rx-cocoa-delegates.md

To subscribe the event you can assign a UITableViewDelegateRx

var tvd = new UITableViewDelegateRx ();
Table.Delegate = tvd;
tvd.RowSelectedObs.Subscribe (c => { });

回答3:

Just to make a small update using ReactiveUI version 9.16.6:

Example that lists some cities with theres according postal codes.

=> My ViewController inherites from ReactiveViewController
=> My CityViewModel inherites from ReactiveObject
=> My CityItemViewModel inherites from ReactiveObject

=> My CityTableViewCell inherites from ReactiveTableViewCell

public class CityViewModel : ReactiveObject
{
    private ICityService CityService { get; }

    private SourceCache<CityItemViewModel, int> _citiesCache;
    private IObservable<IChangeSet<CityItemViewModel, int>> _citiesOperations => _citiesCache.Connect();

    public readonly ReadOnlyObservableCollection<CityItemViewModel> Cities;

    public CityViewModel(ICityService cityService)
    {
        CityService = cityService;
    }

    #region CityViewModelCommand
    public ReactiveCommand<CityItemViewModel, Unit> CityClickCommand { get; }
    #endregion

    private async Task<IEnumerable<CityItemViewModel>> SearchCitiesAsync(string searchText, CancellationToken token)
    {
        IEnumerable<CityItemViewModel> items;

        if (string.IsNullOrEmpty(searchText))
            items = await CityService.ToListWithCountryCodeAsync(cancellationToken: token);
        else
            items = await CityService.ToListBySearchWithCountryCodeAsync(searchText, cancellationToken: token);

        _citiesCache.Edit(innerList =>
        {
            innerList.Clear();
            innerList.AddOrUpdate(items);
        });

        return items;
    }
}

public class CityItemViewModel : ReactiveObject
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string PostalCode { get; set; }
    public override string ToString()
        => $"[CityItemViewModel: Id={Id}, Name={Name}, PostalCode={PostalCode}]";

    public CityItemViewModel() : base()
    {

    }
}

In my ViewController's ViewDidLoad method:

 this.WhenActivated((cleanup) =>
            {
                this.Bind(ViewModel,
                        x => x.SearchText,
                        x => x.searchBar.Text)
                    .DisposeWith(cleanup);

                this.WhenAnyValue(v => v.ViewModel.Cities)
                    .BindTo<CityItemViewModel, CityTableViewCell>(tableView, CityTableViewCell.Key, 50, cell => cell.Initialize(),
                        source => source.ElementSelected.InvokeCommand(ViewModel.CityClickCommand))
                    .DisposeWith(cleanup);
            });

In my Initialize method of my UITableViewCell:

public void Initialize()
        {
            this.WhenAnyValue(v => v.ViewModel.Name)
                .Subscribe(name => cityLabel.Text = name);

            this.WhenAnyValue(v => v.ViewModel.PostalCode)
                .Subscribe(x => postalCodeLabel.Text = x);
        }

Hope that can help someone ;)

来源：https://stackoverflow.com/questions/35750732/how-does-reactivetableviewsourcetsource-work

标签

mvvm