SwiftUI warning - publishing changes within a view (Xcode b5)

[sonisan]

How frequently does the bug occur?

All the time

Description

Using Xcode beta 5 triggers the following SwiftUI warnings:

[SwiftUI] Publishing changes from within view updates is not allowed, this will cause undefined behavior.

No warning was present in the previous beta 3.
My project uses Realm Sync with the @AutoOpen property wrapper. Besides the warning, the code is working as intended.

Stacktrace & log output

Warnings lead to the following block of code:

...
 @Published var asyncOpenState: AsyncOpenState = .connecting {
        willSet {
            objectWillChange.send() // <--- HERE
        }
    }

...
 private func asyncOpenForUser(_ user: User) {
        asyncOpenState = .connecting // <--- HERE

....

Can you reproduce the bug?

Yes, always

Reproduction Steps

Launch the complete code example from the SwiftUI quickstart on https://www.mongodb.com/docs/realm/sdk/swift/swiftui-tutorial/#complete-code

Version

10.28.5

What SDK flavour are you using?

MongoDB Realm (i.e. Sync, auth, functions)

Are you using encryption?

No, not using encryption

Platform OS and version(s)

macOS 12.5

Build environment

Xcode version: 14.0 beta 5

[QuietRocket]

I am experiencing the same warning when using @ObservedResults. Also seems to have no effect on the resulting program, but mentioning "undefined behavior" is slightly worrisome.

The code causing the warning is line 205 in ObservableStoragePublisher.

    func send() {
        subscribers.forEach {
            _ = $0.receive() // <- This one
        }
    }

It might be worth noting that I am not using any sync features, just a local database.

[drmarkpowell]

me too +1

[drmarkpowell]

Still happening Xcode 14 beta 6, RealmSwift 10.28.6 macOS Monterey 12.5

[sonisan]

In my case, it seemed to be tied to @AutoOpen and @AsyncOpen property wrappers. I refactored my authentication flow without them (using let realm = try await Realm(configuration: configuration) and the warnings disappeared.

[robsontenorio]

Still happening Xcode 14 beta 6, RealmSwift 10.28.6 macOS Ventura 13

[QuietRocket]

Hello. This issue was opened over a month ago. Will it be addressed?

iOS 16 is out now, and developers want to upload/update their Realm apps. If we can at least have a statement that this warning is negligible (if that is that case) it would be very comforting. Thank you.

[BugMonkey]

this also affects navigationLink push in iOS16

[stremblayiOS]

+1

[reinosutisno]

+1

[sonisan]

@dianaafanador3 ?

[ejm01]

I've still been trying to figure out what's happening here. A couple of others have some interesting ideas. The issue seems to be affecting all developers, not just ones using Realm.
One interesting theory here (and elsewhere) says SwiftUI4 may intend for developers to not bind published variables...but I think that'd be odd for Apple to do?

If this warning is on purpose, and we're not supposed to bind published variables, I'm still thinking about what our team can do. But my first guess is this an Apple bug, especially given some reports say the warning can be suppressed by changing button styles.

[drmarkpowell]

@ericjordanmossman It looks like your intuition may be right on target regarding this issue.

Donny Wals tweet earlier today: "Heck yes! Xcode 14.1 Beta 3 (finally) fixed the "Publishing changes from within view updates is not allowed, this will cause undefined behavior" bug in SwiftUI https://www.donnywals.com/xcode-14-publishing-changes-from-within-view-updates-is-not-allowed-this-will-cause-undefined-behavior/ "