Get BindingTarget in nested MvxDialogViewController in MvxCollectionViewCell - xamarin.ios

Question

I have a ViewModel called LocationsViewModel, in which I have a ObservableCollection<LocationViewModel>. Additionally I have a LocationsView, which is an MvxCollectionViewController, in which I create a binding set and bind a MvxCollectionViewSource to the ObservableCollection.
In the LocationCell, which is a MvxCollectionViewCell, I want to display a MonoTouch.Dialog which is bound to various properties in the currently
selected LocationViewModel. The easiest way seems to be to create a nested MvxDialogViewController in the MvxCollectionViewCell, however to bind the
Elements in the MvxDialogViewController, I obviously need to create a Binding Target. My question is really can I pass a binding target from the MvxCollectionViewCell to the MvxDialogViewController?
Let me also try to explain it briefly with some code to improve the understanding.
LocationsViewModel.cs
public class LocationsViewModel : MvxViewModel
{
...
public ObservableCollection<LocationViewModel> Locations
{
get { return _locationDataService.Locations.Locations; }
}
...
}
LocationViewModel.cs
public class LocationViewModel : MvxNotifyPropertyChanged
{
...
//Tons of public properties like:
public string Name
{
get { return LinkedDataModel.Name; }
set
{
LinkedDataModel.Name = value;
RaisePropertyChanged(() => Name);
}
}
public double CurrentNoiseLevel
{
get { return LinkedDataModel.CurrentNoiseLevel; }
set
{
LinkedDataModel.CurrentNoiseLevel = value;
RaisePropertyChanged(() => CurrentNoiseLevel);
}
}
...
}
LocationsView.cs
[Register("LocationView")]
public class LocationsView
: MvxCollectionViewController
{
static readonly NSString LocationCellId = new NSString("LocationCell");
private readonly bool _isInitialized;
public LocationsView()
: base(new UICollectionViewFlowLayout()
{
MinimumInteritemSpacing = 0f,
ScrollDirection = UICollectionViewScrollDirection.Horizontal,
MinimumLineSpacing = 0f
})
{
_isInitialized = true;
ViewDidLoad();
}
public new LocationsViewModel ViewModel
{
get { return (LocationsViewModel)base.ViewModel; }
set { base.ViewModel = value; }
}
public sealed override void ViewDidLoad()
{
if (!_isInitialized)
return;
base.ViewDidLoad();
CollectionView.RegisterClassForCell(typeof(LocationCell), LocationCellId);
var source = new MvxCollectionViewSource(CollectionView, LocationCellId);
CollectionView.Source = source;
CollectionView.PagingEnabled = true;
var set = this.CreateBindingSet<LocationsView, LocationsViewModel>();
set.Bind(source).To(vm => vm.Locations);
set.Apply();
CollectionView.ReloadData();
}
}
LocationCell.cs
public class LocationCell : MvxCollectionViewCell
{
[Export("initWithFrame:")]
public LocationCell(RectangleF frame)
: base(string.Empty, frame)
{
InitView();
}
public LocationCell(IntPtr handle)
: base(string.Empty, handle)
{
InitView();
}
private void InitView()
{
var cell = new LocationCellDialog();
ContentView.Add(cell.View);
}
public class LocationCellDialog
: MvxDialogViewController
{
public LocationCellDialog()
: base(UITableViewStyle.Grouped, null, true)
{ }
public override void ViewDidLoad()
{
base.ViewDidLoad();
//How do I get the target here?
var target = ??;
Root = new RootElement
{
new Section
{
new StringElement().Bind(target, t => t.Name),
new StringElement().Bind(target, t => t.CurrentNoiseLevel)
}.Bind(target, t => t.Name),
};
}
}
}
So the question is can I simply pass along a binding target from the parent LocationCell to nested LocationCellDialog or is that a no go?

Answer 1

Each bindable view in MvvmCross has its own DataContext
For a top level View this DataContext is the ViewModel
For a Cell within a List, Table or Collection then the DataContext is set to the object in the list which the Cell is currently showing.
If you want to data-bind any property within a Cell to a property path on the DataContext then you can do so using the Fluent binding syntax.
For example, to bind the Text value of a child UILabel called myLabel to a child property Name on a Person in the list you could use:
this.CreateBinding(myLabel).For(label => label.Text).To<Person>(p => p.Name).Apply();
Or if you wanted to bind the Text to the Person itself you could use:
this.CreateBinding(myLabel).For(label => label.Text).Apply();
In your LocationCell I think you are saying you want to bind the DataContext of the nested LocationCellDialog to the DataContext of the containing cell.
To do this you should be able to use:
private void InitView()
{
var cell = new LocationCellDialog();
ContentView.Add(cell.View);
this.CreateBinding(cell).For(cell => cell.DataContext).Apply();
}