I have a couple of side projects going on, although it is always a challenge to find time of them. One of them, SignalPath, is what I created back in 2015. Currently, I have been spending some time to bump the Swift version to 6 which brought a quite a list of errors. In many places I had code what dealt with observing multiple notifications, but of course Swift 6 was not happy about it.

This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters Show hidden characters let handler: (Notification) -> Void = { [weak self] notification in self?.keyboardInfo = Info(notification: notification) } let names: [Notification.Name] = [ UIResponder.keyboardWillShowNotification, UIResponder.keyboardWillHideNotification, UIResponder.keyboardWillChangeFrameNotification ] observers = names.map({ name -> NSObjectProtocol in return NotificationCenter.default.addObserver(forName: name, object: nil, queue: .main, using: handler) // Converting non-sendable function value to '@Sendable (Notification) -> Void' may introduce data races }) view raw Observer.swift hosted with ❤ by GitHub

After moving all of the notification observing to publishers instead, I can ignore the whole sendable closure problem all together.

This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters Show hidden characters Publishers.Merge3( NotificationCenter.default.publisher(for: UIResponder.keyboardWillShowNotification), NotificationCenter.default.publisher(for: UIResponder.keyboardWillHideNotification), NotificationCenter.default.publisher(for: UIResponder.keyboardWillChangeFrameNotification) ) .map(Info.init) .assignWeakly(to: \.keyboardInfo, on: self) .store(in: &notificationCancellables) view raw Observer.swift hosted with ❤ by GitHub

Great, compiler is happy again although this code could cause trouble if any of the notifications are posted from a background thread. But since this is not a case here, I went for skipping .receive(on: DispatchQueue.main). Assign weakly is a custom operator and the implementation looks like this:

This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters Show hidden characters public extension Publisher where Self.Failure == Never { func assignWeakly<Root>(to keyPath: ReferenceWritableKeyPath<Root, Self.Output>, on object: Root) -> AnyCancellable where Root: AnyObject { return sink { [weak object] value in object?[keyPath: keyPath] = value } } } view raw Combine+Weak.swift hosted with ❤ by GitHub

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