Native Source code for CodeSlicing episode on Animated Weather Icons Part 3 - Making it Rain

WeatherIconRainDemoNative.swift

//
//  WeatherIconRainDemoNative.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 28/04/2021.
//  Copyright © 2021 Adam Fordyce. All rights reserved.
//

import SwiftUI

private struct RainElement: View {
    
    var body: some View {
        RainView()
    }
}

private struct RainView: View {
    @State private var animating = false
    var body: some View {
        GeometryReader { (geo: GeometryProxy) in
            RainShape(animatableData: animating ? 1 : 0)
                .stroke(Color.blue, style: .init(lineWidth: geo.size.width * 0.07, lineCap: .round))
        }
        .onAppear {
            withAnimation(Animation.linear(duration: 1).repeatForever(autoreverses: false)) {
                animating = true
            }
        }
    }
}

private struct RainShape: Shape {
    
    var animatableData: CGFloat
    
    func path(in rect: CGRect) -> Path {
        var path = Path()
        
        let yOffset = rect.height * 0.35
        
        let animationOffset = yOffset * animatableData
        
        let col1X = rect.minX + rect.width * 0.3
        let col2X = rect.minX + rect.width * 0.5
        let col3X = rect.minX + rect.width * 0.7

        for row in 0...2 {
            let rowYOffset = CGFloat(row) * yOffset + animationOffset
            
            let drop1Start = CGPoint(x: col1X, y: rect.minY + rect.height * 0.12 + rowYOffset)
            let drop1End = CGPoint(x: col1X, y: rect.minY + rect.height * 0.29 + rowYOffset)
            
            path.move(to: drop1Start)
            path.addLine(to: drop1End)
            
            let drop2Start = CGPoint(x: col2X, y: rect.minY + rect.height * 0 + rowYOffset)
            let drop2End = CGPoint(x: col2X, y: rect.minY + rect.height * 0.15 + rowYOffset)
            
            path.move(to: drop2Start)
            path.addLine(to: drop2End)
            
            let drop3Start = CGPoint(x: col3X, y: rect.minY + rect.height * 0.05 + rowYOffset)
            let drop3End = CGPoint(x: col3X, y: rect.minY + rect.height * 0.2 + rowYOffset)
            
            path.move(to: drop3Start)
            path.addLine(to: drop3End)
        }
        
        return path
    }
}

struct Rain_Previews: PreviewProvider {
    struct Rain_Harness: View {

        var body: some View {
            RainElement()
                .frame(width: 400, height: 400)
        }
    }

    static var previews: some View {
        Rain_Harness()
            .padding(50)
            .previewLayout(.sizeThatFits)
            .previewDevice("iPhone 12 Pro Max")
            .previewDisplayName("iPhone 12 Pro Max")
    }
}