A toggle switch that looks like an Eye opening and closing. Happy Halloween!

Eye.md

EyeView.swift

// Swift toolchain version 5.0
// Running macOS version 10.15
// Created on 10/31/20.
//
// Author: Kieran Brown
//

import SwiftUI

struct EyeOutline: Shape {
    var upperOffset: CGFloat = 0
    var lowerOffset: CGFloat = 0

    var animatableData: AnimatablePair<CGFloat, CGFloat> {
        get {AnimatablePair(upperOffset, lowerOffset)}
        set {
            self.upperOffset = newValue.first
            self.lowerOffset = newValue.second
        }
    }

    func path(in rect: CGRect) -> Path {
        let w = rect.width
        let h = rect.height

        return Path { path in
            path.move(to: CGPoint(x: 0, y: h/2))
            path.addQuadCurve(to: CGPoint(x: w, y: h/2), control: CGPoint(x: w/2, y: h/4))
            path.addQuadCurve(to: CGPoint(x: 0, y: h/2), control: CGPoint(x: w/2, y: h/(4 - 2*upperOffset)))
            path.closeSubpath()
            path.addQuadCurve(to: CGPoint(x: w, y: h/2), control: CGPoint(x: w/2, y: 3*h/4))
            path.addQuadCurve(to: CGPoint(x: 0, y: h/2), control: CGPoint(x: w/2, y: (3-lowerOffset)*h/(4)))
            path.closeSubpath()
        }
    }
}

struct EyeShape: Shape {
    func path(in rect: CGRect) -> Path {
        let w = rect.width
        let h = rect.height

        return Path { path in
            path.move(to: CGPoint(x: 0, y: h/2))
            path.addQuadCurve(to: CGPoint(x: w, y: h/2), control: CGPoint(x: w/2, y: h/4))
            path.addQuadCurve(to: CGPoint(x: 0, y: h/2), control: CGPoint(x: w/2, y: 3*h/4))
            path.closeSubpath()
        }
    }
}

struct EyeView: View {
    @Binding var isOpen: Bool
    let scleraColor = Color.white
    let eyeLidColor = Color(white: 0.8)
    let irisGradient = RadialGradient(
        gradient: Gradient(colors: [Color(red: 0, green: 0.5, blue: 0.8), Color(red: 0.3, green: 0.5, blue: 0.8)]),
        center: .center,
        startRadius: 5,
        endRadius: 100
    )

    var offset: CGFloat { isOpen ? 0.2 : 0.96 }

    var body: some View {
        GeometryReader { proxy in
            ZStack {
                EyeShape()
                    .fill(scleraColor)
                    .shadow(radius: 3)
                Circle()
                    .stroke(irisGradient, lineWidth: 0.7*proxy.size.width/4)
                    .frame(width: proxy.size.width/4)
                EyeOutline(upperOffset: offset,
                           lowerOffset: offset)
                    .fill(eyeLidColor)
                    .overlay(EyeOutline(upperOffset: offset,
                                        lowerOffset: offset)
                                .stroke(eyeLidColor, style: StrokeStyle(lineWidth: 4, lineJoin: .round)))
            }
            .contentShape(Rectangle())
            .onTapGesture(perform: { self.isOpen.toggle() })
            .animation(.spring())
            .frame(width: proxy.size.width,
                   height: proxy.size.width*2)
        }
    }
}

struct EyeExample: View {
    @State var isOpen: Bool = true
    var body: some View {
        EyeView(isOpen: $isOpen).padding()
    }
}

struct EyeView_Previews: PreviewProvider {
    static var previews: some View {
        EyeExample()
    }
}