Dear Experts, I have been looking at thr SimpleWatchConnectivity sample code: https://developer.apple.com/documentation/watchconnectivity/transferring-data-with-watch-connectivity There are a couple of things in there that look out of date. Firstly, it uses a WKApplicationDelegate to receive the background tasks. I believe this can probably be entirely removed, and replaced with .backgroundTask(.watchConnectivity) { ... } on the App. Is that true? What do I need something inside the { ... } there? Secondly, it is using NSNotificationCenter to send received data from the WCSessionDelegate to the SwiftUI view hierarchy. Is there a better way to do that? I have spent a while trying to work out how a WCSessionDelegate class can connect to a binding to a SwiftUI @State property, and cause the UI to update in response to received data, but I haven't made it work. Are there any newer examples of how to do this? I'm currently only trying to send some simple applicationContext state from the phone to the watch and have some views update to show the latest values. Thanks, Phil.

The WatchOS Control Center has an Edit/Done button at the bottom, and in its edit mode, elements can be moved around and added/removed. Yet, the SwiftUI List doesn't have an edit mode on WatchOS. My question is: is the edit functionality in Control Center a custom thing, or is that present in some SwiftUI component that I've missed?

In my Mac's Settings -> General -> Storage -> Developer -> (i) I have a series of entries for "bridgeOS", all 2.49 GB except one that is "zero". Do I need these? Can I remove them? I am only doing "normal" iPhone / iPad development. (There was some previous mention of this here: https://developer.apple.com/forums/thread/711279 with no feedback.)

Is remotepairingd part of Xcode? It seems to be stuck using 119% CPU. This may have started when I recently paired my new Apple Watch with Xcode - or maybe that is a coincidence. The console is full of: error 16:40:26.237601+0000 remotepairingd socket-1: No more data can be received, connection was closed

I'm referring to the use of a "settings bundle" plist to cause the main Settings app to display your app's preferences which the app can then read via NSUserDefaults, as described here: https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/UserDefaults/Preferences/Preferences.html#//apple_ref/doc/uid/10000059i-CH6 I am wondering if this is actually deprecated, or something. I ask because, (1), it still has the high-quality old-style documentation, and (2) there doesn't seem to be a "required reason API" code for using it. Specifically, the NSUserDefaults required reason API codes are CA92.1 : "This reason does not permit reading information that was written by other apps or the system" 1C8F.1 : "This reason does not permit reading information that was written by apps, app extensions, or App Clips outside the same App Group or by the system." C56D.1: "...third-party SDK..." - nope. AC6B.1: "... com.apple.configuration.managed ..." - nope. None of the codes permit reading preferences that have been set by the Settings app using this method.

When my iOS app runs on macOS in "designed for iPad" mode, the system foreground colour RGBA values seem strange. Looking at [UIColor labelColor], [UIColor secondaryLabelColor] etc. on iOS, I see values like these: (Light Mode) // R G B A fg0 = 0 0 0 255 fg1 = 10 10 13 153 fg2 = 10 10 13 76 fg3 = 10 10 13 45 Note in particular that fg0, aka labelColor, is solid black. When I run it on my Mac, the values I see are: // R G B A fg0 = 0 0 0 216 fg1 = 0 0 0 127 fg2 = 0 0 0 66 fg3 = 0 0 0 25 Here, fg0 has alpha = 216. The result is that it looks like a dark grey, on a white background. Of course it's reasonable for macOS to have a different colour palette than iOS - but native macOS apps seem to have solid 100% black as their foreground colour. Do others see this? What should I be doing? Note that I'm getting colour values using UIColor's getRed: blue: green: alpha: method and then using these colour values for some custom GPU drawing. Previously I was using solid black and white, but at some point I updated it to use UIColor in order to respond to light/dark-mode changes.

I have a rather simple StoreKitSubscriptionView for my app's single subscription. Question: Am I expected to write code to handle lack of network connectivity? When I run the app on development device, not using the local StoreKit configuration but rather the real app store, if the network is not available I get a not-user-friendly error message instead of the normal SubscriptionStoreView content. I'm uncertain if end-users actually see this. Maybe they see a more appropriate "Cannot connect to App Store, try later" message? Maybe I am supposed to check for network and not present the view if it is not available. I don't recall any mention of this in the WWDC video but I guess I should check again. Ideas anyone?

Consider this Swift struct: public struct Example { public func foo(callback: ()->Void) { .... } public func blah(i: Int) { .... } .... } Using Swift/C++ interop, I can create Example objects and call methods like blah. But I can't call foo because Swift/C++ interop doesn't currently support passing closures (right?). On the other hand, Swift/objC does support passing objC blocks to Swift functions. But I can't use that here because Example is a Swift struct, not a class. So I could change it to a class, and update everything to work with reference rather than value semantics; but then I also have to change the objC++ code to create the object and call its methods using objC syntax. I'd like to avoid that. Is there some hack that I can use to make this possible? I'm hoping that I can wrap a C++ std::function in some sort of opaque wrapper and pass that to swift, or something. Thanks for any suggestions!

I’ve just tried to reply to a post and I get an “unauthorized” error page back. I’m logged in. I’m posting from an iPad, which is unusual, I normally use my Mac. This post is in part to see if I can post at all, or whether it was just that one reply that is. not working.

I would like to be able to write something like: struct FooView: View { let foo: Foo; var body: some View { assert(foo.valid); ...... } }; but of course I can't, because "Type () cannot conform to View". What's the best way to achieve this?

I have a simple SwiftUI Text: Text(t) .font(Font.system(size: 9)) Strangely its ideal height seems to be larger when it is empty. I initially observed this in a custom Layout container that wasn't working quite right. Eventually I looked at the height returned by v.dimensions(in:), and found that when t is non-empty the height is 11; when empty, it's 14. Subsequently I observed similar behaviour in a regular VStack container. Has anyone seen anything similar? Are there any properties that could affect this behaviour? (This is on a watch - I don't know if that matters.)

I'm struggling to implement a flash animation in SwiftUI. Generally animations animate from one value to another. I'd like to animate from normal to the flashed state and then back to normal, each time the data shown by the view changes. The "flashed state" could be transparent, or a white background, or it could be a scale change for a pulse effect, or something. Example: struct MyView: View { let value: String; var body: some View { ZStack { Capsule() .fill(Color.green); Text(value); } }; }; Each time value changes, I'd like the colour of the capsule to quickly animate from green to white and back to green. I feel this should be easy - am I missing something? For bonus points: I'd like the Text to change to its new value at the midpoint of the animation, i.e. when the white text is invisible on the white background. I'd like to get the flash effect whenever I have a new value even if the new value is equal to the old value, if you see what I mean.

I have a grid-like container with subviews. I recently changed some internal details of the subviews, so that changes to the values they display animate. Now, the behaviour of the grid container has changed: the animation duration used for the internal changes is now also used when the grid is re-ordered or subviews are added or removed. I can see why this happens: the grid repositions the subviews, and the subview has declared an animation that applies to all of its properties however they are modified. This doesn't seem like a good idea to me. The principle of encapsulation suggests that I should be able to make internal changes to a component without suffering "spooky action at a distance", i.e. other components unexpectedly changing their behaviour. Is this an inherent issue with SwiftUI animations, or does it suggest that I am doing something wrong?

How do I draw a single line of text in a SwiftUI Canvas, scaled to fill a given rectangle? Example: Canvas { context, size in let r = CGRect(origin: CGPointZero, size: size); // Whole canvas let t = Text("Hello World"); context.draw(t, in: r); } Outside of Canvas I'd add .minimumScaleFactor(0) .lineLimit(1), and I guess set a large default font size, and I'd get the result I want. But inside Canvas, .minimumScaleFactor and .lineLimit don't seem to be available; they return some View, not Text, which can't be used in context.draw. (Is there a trick to make that work?) I have written the following to do this, but I think there must be an easier way to achieve this! Suggestions? extension GraphicsContext { mutating func draw_text_in_rect(string: String, rect: CGRect) { let text = Text(string) .font(.system(size: 25)); // The font size used here does matter, because e.g. letter spacing // varies with the font size. let resolved = resolve(text); let text_size = resolved.measure(in: CGSize(width: CGFloat.infinity, height: CGFloat.infinity)); let text_aspect = text_size.width / text_size.height; let fit_size = CGSize(width: min(rect.size.width, rect.size.height*text_aspect), height: min(rect.size.height, rect.size.width/text_aspect)); let fit_rect = CGRect(x: rect.origin.x + (rect.size.width-fit_size.width)/2, y: rect.origin.y + (rect.size.height-fit_size.height)/2, width: fit_size.width, height: fit_size.height); let scale = fit_size.width / text_size.width; // For debug: // var p = Path(); // p.addRect(fit_rect); // stroke(p, with: GraphicsContext.Shading.color(.red), lineWidth: 1); translateBy(x: fit_rect.minX, y: fit_rect.minY); scaleBy(x:scale, y:scale); draw(resolved, at: CGPointZero, anchor: UnitPoint.topLeading); transform = CGAffineTransformIdentity; } };

There doesn't seem to be a background mode that will allow an iPhone app to run in the background in order to communicate with its watch app, which is running in the foreground on the watch. Have I missed something? Related but not quite the same: say the iPhone app can run in the background to get location updates. But it only wants to do so when the watch app is running. Is there a way that the watch app can wake, or even start, the iPhone app, and for the iPhone app to then enable location updates? (I have previously implemented Bluetooth background modes - I think I could achieve both of the above if I had the watch and the iPhone communicate using my own BTLE protocol, rather than using Watch Connectivity. Is this true?)