/// <summary>
/// Applies an <see cref="InstancedBinding"/> a property on an <see cref="IAvaloniaObject"/>.
/// </summary>
/// <param name="target">The target object.</param>
/// <param name="property">The property to bind.</param>
/// <param name="binding">The instanced binding.</param>
/// <param name="anchor">
/// An optional anchor from which to locate required context. When binding to objects that
/// are not in the logical tree, certain types of binding need an anchor into the tree in
/// order to locate named controls or resources. The <paramref name="anchor"/> parameter
/// can be used to provide this context.
/// </param>
/// <returns>An <see cref="IDisposable"/> which can be used to cancel the binding.</returns>
public static IDisposable Apply(
IAvaloniaObject target,
AvaloniaProperty property,
InstancedBinding binding,
object anchor)
{
Contract.Requires <ArgumentNullException>(target != null);
Contract.Requires <ArgumentNullException>(property != null);
Contract.Requires <ArgumentNullException>(binding != null);
var mode = binding.Mode;
if (mode == BindingMode.Default)
{
mode = property.GetMetadata(target.GetType()).DefaultBindingMode;
}
switch (mode)
{
case BindingMode.Default:
case BindingMode.OneWay:
return(target.Bind(property, binding.Observable ?? binding.Subject, binding.Priority));
case BindingMode.TwoWay:
return(new CompositeDisposable(
target.Bind(property, binding.Subject, binding.Priority),
target.GetObservable(property).Subscribe(binding.Subject)));
case BindingMode.OneTime:
var source = binding.Subject ?? binding.Observable;
if (source != null)
{
return(source
.Where(x => BindingNotification.ExtractValue(x) != AvaloniaProperty.UnsetValue)
.Take(1)
.Subscribe(x => target.SetValue(property, x, binding.Priority)));
}
else
{
target.SetValue(property, binding.Value, binding.Priority);
return(Disposable.Empty);
}
case BindingMode.OneWayToSource:
return(Observable.CombineLatest(
binding.Observable,
target.GetObservable(property),
(_, v) => v)
.Subscribe(x => binding.Subject.OnNext(x)));
default:
throw new ArgumentException("Invalid binding mode.");
}
}
/// <summary>
/// Applies an <see cref="InstancedBinding"/> a property on an <see cref="IAvaloniaObject"/>.
/// </summary>
/// <param name="target">The target object.</param>
/// <param name="property">The property to bind.</param>
/// <param name="binding">The instanced binding.</param>
/// <param name="anchor">
/// An optional anchor from which to locate required context. When binding to objects that
/// are not in the logical tree, certain types of binding need an anchor into the tree in
/// order to locate named controls or resources. The <paramref name="anchor"/> parameter
/// can be used to provide this context.
/// </param>
/// <returns>An <see cref="IDisposable"/> which can be used to cancel the binding.</returns>
public static IDisposable Apply(
IAvaloniaObject target,
AvaloniaProperty property,
InstancedBinding binding,
object?anchor)
{
_ = target ?? throw new ArgumentNullException(nameof(target));
_ = property ?? throw new ArgumentNullException(nameof(property));
_ = binding ?? throw new ArgumentNullException(nameof(binding));
var mode = binding.Mode;
if (mode == BindingMode.Default)
{
mode = property.GetMetadata(target.GetType()).DefaultBindingMode;
}
switch (mode)
{
case BindingMode.Default:
case BindingMode.OneWay:
if (binding.Observable is null)
{
throw new InvalidOperationException("InstancedBinding does not contain an observable.");
}
return(target.Bind(property, binding.Observable, binding.Priority));
case BindingMode.TwoWay:
if (binding.Subject is null)
{
throw new InvalidOperationException("InstancedBinding does not contain a subject.");
}
return(new TwoWayBindingDisposable(
target.Bind(property, binding.Subject, binding.Priority),
target.GetObservable(property).Subscribe(binding.Subject)));
case BindingMode.OneTime:
var source = binding.Subject ?? binding.Observable;
if (source != null)
{
// Perf: Avoid allocating closure in the outer scope.
var targetCopy = target;
var propertyCopy = property;
var bindingCopy = binding;
return(source
.Where(x => BindingNotification.ExtractValue(x) != AvaloniaProperty.UnsetValue)
.Take(1)
.Subscribe(x => targetCopy.SetValue(
propertyCopy,
BindingNotification.ExtractValue(x),
bindingCopy.Priority)));
}
else
{
target.SetValue(property, binding.Value, binding.Priority);
return(Disposable.Empty);
}
case BindingMode.OneWayToSource:
{
if (binding.Observable is null)
{
throw new InvalidOperationException("InstancedBinding does not contain an observable.");
}
if (binding.Subject is null)
{
throw new InvalidOperationException("InstancedBinding does not contain a subject.");
}
// Perf: Avoid allocating closure in the outer scope.
var bindingCopy = binding;
return(Observable.CombineLatest(
binding.Observable,
target.GetObservable(property),
(_, v) => v)
.Subscribe(x => bindingCopy.Subject.OnNext(x)));
}
default:
throw new ArgumentException("Invalid binding mode.");
}
}