SwiftUI example showing a sticky state drag with spring animations

StickyDrag.swift

//
//  StickyDrag.swift
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
//  of the Software, and to permit persons to whom the Software is furnished to do so,
//  subject to the following conditions:

//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
//  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
//  PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
//  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
//  AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
//  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
//  Created by Adam Fordyce on 10/01/2020.
//  Copyright © 2020 Adam Fordyce. All rights reserved.
//

import SwiftUI
import PureSwiftUI

struct StickyDrag: View {
 
    var body: some View {
        HStack {
            StickyShape(color: .red)
            StickyShape(color: .green)
            StickyShape(color: .blue)
        }
    }
}

private let stickyThreshold: CGFloat = 175
private let shapeSize: CGFloat = 100

struct StickyShape: View {
    
    let color: Color
    
    @GestureState private var translation: CGSize = .zero
    
    var scaleForTranslation: CGFloat {
        if abs(translation.y) < stickyThreshold {
            return 1 + abs(translation.y) / shapeSize
        } else {
            return 1
        }
    }
    
    var offsetForTranslation: CGFloat {
        if abs(translation.y) < stickyThreshold {
            return translation.y / 2
        } else {
            return translation.y
        }
    }
    
    var body: some View {
        VStack {
            Frame(shapeSize, self.color)
                .shadow(5)
                .yScale(self.scaleForTranslation)
                .yOffset(self.offsetForTranslation)
                .gesture(DragGesture(minimumDistance: 0)
                    .updating(self.$translation) { value, state, _ in
                    state = value.translation
                })
                .animation(.spring(response: 0.2, dampingFraction: 0.4, blendDuration: 1))
        }
    }
}

struct StickyDrag_Previews: PreviewProvider {
    struct StickyDrag_Harness: View {
        
        var body: some View {
            StickyDrag().previewDevice(.iPhone_11_Pro)
        }
    }
    
    static var previews: some View {
        StickyDrag_Harness()
    }
}