GeometryReader 胸熱struct ContentView : View { @State var int = 0 var body: some View { let red = int > 0 Text("Hello World") .background(red ? Color.red : Color.blue) } } ↑はビルドエラーになるけど struct ContentView : View { @State var int = 0 var red: Bool { int > 0 } var body: some View { Text("Hello World") .background(red ? Color.red : Color.blue) } } ならOKですね