///<summary>
/// Activates a child whenever the specified parent is activated.
/// Use with caution, it is better to use explicit <see cref="IConductor"/> implementations.
///</summary>
///<param name="child">The child to (de)activate.</param>
///<param name="parent">The parent whose activation triggers the child's activation.</param>
public static void ActivateWith(this IActivate child, IActivate parent)
{
if (parent == null)
{
return;
}
// Note on the disposal, in a hierarchical composition we'll always want to close the child(ren) first.
// Eg in a multilevel tree the leaf nodes will be closed first, working our way back to the root.
child.Activator.AddDisposable(
parent.WhenAnyValue(x => x.IsActive)
.Where(isActive => isActive)
.Select(_ => child.ActivateAsync(CancellationToken.None)) // Tasks are executed eagerly, fire and forget
.Subscribe()
);
}