Issue 70  21st January 2025

Solving “Main actor-isolated property can not be referenced from a Sendable closure” in Swift – Donny Wals

I am pretty sure you have run into "Main actor-isolated property can not be referenced from a Sendable closure" if you've turned on strict concurrently checking or Swift 6 language mode for your code base.

Donny walks through several options to resolve this error, and explains when you should use each of them.

I had the opportunity to attend Donny's workshop about Swift concurrency at Do iOS last year, and this is one of the exercises that we worked through. I can warmly recommend this workshop, so if you get a chance to attend it, go for it!

donnywals.com  

Using withObservationTracking to monitor changes in @Observable properties outside SwiftUI views

The Observation framework, introduced at WWDC 23, was primarily intended to allow for a more fine grained property observation in SwiftUI, allowing SwiftUI to update only the views that required updating.

But Observation can also be used outside the context of SwiftUI. Natalia and Mat wrote about this before, and showed how you can use the Observation framework outside of SwiftUI, and how you can create an AsyncStream from withObservationTracking.

Looking at the signature of `withObservationTracking, you can't help but think that this was never intended to be used outside of Apple's own frameworks: it's hard to understand what this function really does, let alone how to properly use it. That's probably one of the reasons there are so many blog posts about it...

Pol ran into the same issue, and came up with an improved version of the function that has a much better developer experience. Here is how the call site looks like:

withObservationTracking(of: model.value) {
  print($0)
}

Much cleaner, don't you think? Read the full article here.

polpiella.dev  

How to hide private information using the privacySensitive view modifier

In this article, Vincent explains how to use the privacySensitive view modifier to hide sensitive data when the app goes into the background, and then goes on to show how you can work around some of the limitations of this view modifier by introducing your own custom modifier.

Paul shows how you can use the redactionReasons environment value to provide a custom layout if the system applies the privacy redaction reason in this article.

And if you want to prevent the system from taking a screenshot of sensitive views, Giovanni has you covered as well.

Also, did you know you can use isSceneCaptured to find out if the current scene is being projected (e.g. via AirPlay), mirrored, or recorded?

swiftwithvincent.com