[BUG] UIKit.UIKitThreadAccessException in iOS as canExecute: this.IsValid() doesn't tick in MainThread

[gsgou]

Describe the bug
UIKit.UIKitThreadAccessException in iOS as canExecute: this.IsValid() doesn't tick in MainThread

Steps To Reproduce
Bind Command to any Xamarin Forms Button,
SomeCommand = ReactiveCommand.CreateFromObservable(
observable,
canExecute: this.IsValid());
UIKit.UIKitThreadAccessException is thrown

Expected behavior
No thrown UIKit.UIKitThreadAccessException

Environment

• OS: iOS 13.4
• Version: Xamarin Forms 4.4.0.991864, Xamarin.iOS 13.16.0.13
• Working Version: unknown

Additional context
Workaround:

SomeButtonCommand = ReactiveCommand.CreateFromObservable(
    observable,
    canExecute: this.IsValid().ObserveOn(RxApp.MainThreadScheduler));

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[michaelstonis]

@gsgou this is expected behavior. ReactiveCommands do not explicitly schedule anything on the UI thread. Since CanExecute controls whether a button is enabled/disabled, if you use the BindCommand extension, you need to ensure that the observable that controls CanExecute pushes the notification on the UI thread. Not all commands need to notify on UI thread, so there is no blanket policy to apply or force that on any of the Bind or BindCommand extensions.

[gsgou]

@michaelstonis tks a lot, i get it now.
Maybe the Sample could be updated for XF then
and an overload of the IsValid() with a scheduler.

[github-actions]

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