Jump.swift

//
//  ContentView.swift
//  Shared
//
//  Created by Chris Eidhof on 16.04.22.
//

import SwiftUI

struct Jump: AnimatableModifier {
    var progress: Double = 0
    var amplitude: CGFloat = 20
    
    var animatableData: Double {
        get { progress }
        set { progress = newValue }
    }
    
    func body(content: Content) -> some View {
        // We only jump for the first half of the animation, after that we stay in place
        let jumpProgress = progress < 0.5 ? progress * 2 : 1
        content.offset(y: -sin(.pi * jumpProgress) * amplitude)
    }
}

extension View {
    func jump(_ active: Bool, amplitude: CGFloat = 20) -> some View {
        modifier(Jump(progress: active ? 1 : 0, amplitude: amplitude))
    }
}

struct ContentView: View {
    @State var active = false
    var body: some View {
        Text("Hello, world!")
            .jump(active)
            .animation(.linear(duration: 2).repeatForever(autoreverses: false), value: active)
            .padding(50)
            .onAppear {
                active = true
            }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}