Hey guys,

I'm pretty new to SwiftUI therefore I'm not a big help fixing this, but I noticed that when changing the URL of the AsyncImage the new URL is not downloaded an displayed. I'm guessing the view needs to be destroyed first?

Here is what I'm using and what does not work:

...
if(libraryArtwork != nil) {
            AsyncImage(url: libraryArtwork!.artworkUrl(width: urlResolution(), height: urlResolution())!, content: { image in
                image.resizable()
            }, placeholder: {
                Rectangle().frame(width: width, height: width).foregroundColor(.gray)
            }).frame(width: width, height: width)
        } else {
            Rectangle().frame(width: width, height: width).foregroundColor(.gray)
        }
...

So in this case the libraryArtwork might be changed externally because it is coming from the viewModel.

Is the intended behaviour. Can I fix this somehow?

$swift --version
swift-driver version: 1.45.2 Apple Swift version 5.6.1 (swiftlang-5.6.0.323.66 clang-1316.0.20.12)
Target: arm64-apple-macosx12.0

$xcodebuild -version 
Xcode 13.4
Build version 13F17a

Refs

* https://github.com/apple/swift-package-manager/pull/2674
* https://github.com/apple/swift-package-manager/pull/3511
* https://github.com/apple/swift-package-manager/pull/3468

Runtime error

Accessing StateObject's object without being installed on a View. This will create a new instance each time.

Solution

• https://forums.swift.org/t/explanation-behind-the-error-accessing-stateobjects-object-without-being-installed-on-a-view-this-will-create-a-new-instance-each-time/40111

With this implementation, ContentView body will be redrawn each time a button is pressed. Then, @ObserbedObject is also regenerated, and AsyncImagePhase revert to empty.

struct ContentView: View {
    @State var count: Int = 0

    var body: some View {
        VStack {
            AsyncImage(url: URL(string: "https://example.com/icon.png"))
            Button {
                count += 1
            } label: {
                Text("Count: \(count)")
            }
        }
    }
}

This issue can be avoided by changing @ObserbedObject to @StateObject. However, @StateObject is not available on iOS 13/macOS 10.15/tvOS 13/watchOS 6, so resolved it using @State.

References

• https://kouki.hatenadiary.com/entry/2021/06/22/130000
• https://github.com/ra1028/SwiftUI-Hooks/blob/main/Sources/Hooks/HookScope.swift

Hello.

I'm using your package in a project and I noticed that Xcode gives the warning:

"Accessing StateObject's object without being installed on a View. This will create a new instance each time."

at the point where self.viewModel.download() is called, inside a view initialiser.

That's happening because the download is being initiated when the view is initialised rather than when it's added to the view hierarchy. I think you should consider fixing your implementation by moving all the self.viewModel.download() calls out of the initialisers they're in and into a closure passed to an onAppear() view modifier, like so:

init(viewModel: ViewModel,
     @ViewBuilder content: @escaping (AsyncImagePhase) -> Content) {
    self._viewModel = .init(wrappedValue: viewModel)
    self.content = content
    // self.viewModel.download() // <--- remove this line
}

var body: some View {
    content(viewModel.phase)
        .onAppear { viewModel.download() } // <--- add this line
}

In any case, thanks for writing this package.

https://developer.apple.com/documentation/swiftui/asyncimage/init(url:scale:)

scale The scale to use for the image. The default is 1. Set a different value when loading images designed for higher resolution displays. For example, set a value of 2 for an image that you would name with the @\2x suffix if stored in a file on disk.

• [x] iOS
• [ ] macOS
• [x] tvOS
• [x] watchOS