【Swift UI】withAnimationの使い方！アニメーションを実装する

func withAnimation<Result>(
    _ animation: Animation? = .default,
    _ body: () throws -> Result
) rethrows -> Result

struct ContentView: View {
    
    @State  private var opacity: Double = 0.0
    
    var body: some View {
        VStack {
            Button {
                withAnimation {
                    opacity = opacity == 1 ? 0 : 1
                }
            } label: {
                Text("Action")
            }
            Text("Hello")
                .padding()
                .background(Color.cyan)
                .cornerRadius(10)
                .opacity(opacity)
        }
    }
}

withAnimation(Animation.easeIn) {
    // 
}

withAnimation(Animation.easeIn.delay(2)) {
  // 
}

withAnimation(Animation.linear(duration: 3)) {
  //
}

struct ContentView: View {
    
    @State  private var show:Bool = false
    
    var body: some View {
        VStack {
            Button {
                withAnimation {
                    show.toggle()
                }
            } label: {
                Text("Action")
            }
            if show {
                Text("Hello")
                    .padding()
                    .background(Color.cyan)
                    .cornerRadius(10)
                    .transition(.scale)
            }
        }
    }
}

nonisolated
func animation<V>(
    _ animation: Animation?,
    value: V
) -> some View where V : Equatable

struct ContentView: View {
    @State  private var opacity: Double = 0.0

    var body: some View {
        VStack {
            Button {
                opacity = opacity == 1 ? 0 : 1
            } label: {
                Text("Animate")
            }
            
            Text("Hello")
                .padding()
                .background(Color.cyan)
                .cornerRadius(10)
                .opacity(opacity)
                .animation(.easeInOut(duration: 1.0), value: opacity)
        }
    }
}