SwiftUI Tips

Posted on Edited on Disqus: Word count in article: 2k Reading time ≈ 2 mins.

Binding to UserDefaults

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class UD: ObservableObject {
    @Published var date: Date = UserDefaults.standard.value(forKey: "date") as? Date ?? Date() {
        didSet {
            UserDefaults.standard.set(self.date, forKey: "date")
        }
    }
}

AppDelegate -> SceneDelegate

Many Delegates moved from AppDelegate.swift to SceneDelegate.swift

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func application(_ app: UIApplication, open url: URL, options: [UIApplication.OpenURLOptionsKey : Any] = [:]) -> Bool {

}
// to
func scene(_ scene: UIScene, openURLContexts URLContexts: Set<UIOpenURLContext>) {

}
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struct ContentView: View {
    @EnvironmentObject var ud: UD

    var body: some View {
        let url = "Title:status?date=\(String(ud.firstDate.timeIntervalSince1970))"
        return NavigationView {
            VStack {
                qrCodeImage(for: url)!

                Spacer().frame(height: 50)

                Text("\(ud.firstDate)")
            }.navigationBarTitle("Title")
                .navigationBarItems(trailing:
                    HStack {
                        NavigationLink(destination: PickerView(date: $ud.firstDate)) {
                            Image(systemName: "gear")
                        }
                    }
            )
        }
    }
}

PickerView Binding

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struct PickerView: View {
    @Binding var date: Date

    var body: some View {
        return NavigationView {
            VStack {
                DatePicker(selection: $date, in: ...Date(), displayedComponents: .date) {
                    Text("")
                }
            }
        }
    }
}

Fix SwiftUI Image Blank View

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var ciContext = CIContext()

func qrCodeImage(for string: String) -> Image? {
    let data = string.data(using: String.Encoding.utf8)
    guard let qrFilter = CIFilter(name: "CIQRCodeGenerator") else { return nil }
    qrFilter.setValue(data, forKey: "inputMessage")

    let transform = CGAffineTransform(scaleX: 10, y: 10)

    guard let ciImage = qrFilter.outputImage?.transformed(by: transform) else {
        return nil
    }

    let cgImage = ciContext.createCGImage(ciImage, from: ciImage.extent)
    // convert to UIImage
    let uiImage = UIImage(cgImage: cgImage!)
    let image = Image(uiImage: uiImage)

    return image
}

Translated by gpt-3.5-turbo