View+Extensionにレイアウトに関する関数を実装しました。

@YusukeHosonuma
初めまして、TwitterでのiOS/SwiftUIに関する情報発信にいつも感謝しております。 私がSwiftUIの開発で普段使っているものをご提案させていただければかと思います。 （といっても、いつもチェックしている海外サイトのコピーコードなのですが。）

引用元

https://kavsoft.dev/

struct ContentView: View {
    var body: some View {
          Color.blue
              .invertedMask {
                  Image(systemName: "swift")
                      .resizable()
                      .scaledToFit()
                      .frame(width: 200, height: 200)
              }
    }
}

struct ContentView: View {
    var body: some View {
        Text("Hello")
            .onReceive(notification: UIScene.didEnterBackgroundNotification) { notification in
                print("\(notification)")
            }
    }
}

struct AlertView: View {
    @State var error: MyError? = nil

    var body: some View {
        VStack {
            ControlGroup {
                Button("Warning") { error = .warning }
                Button("Fatal") { error = .fatal }
            }
            .padding()
        }
        .alert(error: $error) {} // ✅
    }
}

//
// ✅ Print `offset` when it changed.
//
.printOnChange("🍎") { offset }
//
// ☑️ Equivalent to the following.
//
.onChange(of: offset) {
    print("🍎\($0)")
}

e.g.

image
    .onChangeSize {
        imageSize = Self.calculateImageSize(
            bounds: geometry.size,
            originalSize: $0,
            contentMode: contentMode
        )
    }

ResizableImage

Resize only if the area overflows. (show as original-size if it included in area)

• View
  • original(or contentMode: ContentMode) -> some View

Extension

• CGSize
  • contains(_ other: CGSize) -> Bool
• View
  • frame(size: CGSize?) -> some View
  • sizePreference() -> some View
  • onChangeSizePreference(_ perform: @escaping (CGSize) -> Void) -> some View
• View (iOS 15+)
  • boundsPreference() -> some View
  • onChangeBoundsPreference(_ geometry: GeometryProxy, perform: @escaping (CGSize) -> Void) -> some View

struct BindingMapView: View {
    @State var boolString = "false"

    var body: some View {
        VStack {
            TextField("isOn", text: $boolString)
                .textFieldStyle(.roundedBorder)
                .autocapitalization(.none)

            //
            // 💡 Can edit `String` as `Bool`.
            //
            Toggle("isOn", isOn: $boolString.map( // ✅ `Binding<String>` -> `Binding<Bool>`
                get: { $0 == "true" },
                set: { $0 ? "true" : "false" }
            ))
        }
        .padding()
    }
}

struct CaseBindingView: View {
    @State var value: EnumValue = .string("Swift")

    var body: some View {
        VStack(alignment: .center) {
            //
            // 💡 Note: `switch` statement is only for completeness check by compiler.
            // (Removal does not affect the operation)
            //
            switch value {
            case .string:
                //
                // ✅ Binding<Value> -> Binding<String>?
                //
                if let binding = $value.case(/EnumValue.string) {
                    TextField("placeholder", text: binding)
                }

            case .bool:
                //
                // ✅ Binding<Value> -> Binding<Int>?
                //
                if let binding = $value.case(/EnumValue.bool) {
                    Toggle("isOn", isOn: binding)
                }
            }
            ...
        }
    }
}

#if os(macOS)
private typealias XImage = NSImage
#else
private typealias XImage = UIImage
#endif

struct ImageView: View {
    var body: some View {
        Image(image: renderImage()) // ✅
            .resizable()
            .scaledToFit()
    }

    private func renderImage() -> XImage {
        // ⚠️ Assumes rendering code
        #if os(macOS)
        NSImage(named: "picture")!
        #else
        UIImage(named: "picture")!
        #endif
    }
}

Usage:

private struct OptionalTextEditView: View {
    @Binding var optionalString: String? // 💡 `Binding<String?>`

    var body: some View {
        //
        // ✅ `Binding<String?>` -> `Binding<String>?`
        //
        if let binding = $optionalString.wrappedBinding() {
            TextField("placeholder", text: binding) // 💡 require `Binding<String>`
                .textFieldStyle(.roundedBorder)
                .padding(.horizontal)
        } else {
            Text("nil")
        }
    }
}