SimpleAnimation.swift

import SwiftUI

struct SimpleAnimation: View {
    // In Xcode preview? animation doesn't work
    // animate only if these are set to true
    // why when set to false, no animation?
    @State var flag = false
    @State var anotherFlag = true

    var body: some View {
        ZStack {

            // add this ZStack, `if flag` animation only animates true branch, not false branch
//            ZStack {
//                Color.green
////                if flag {
////                    Color.blue
////                } else {
////                    Color.green
////                }
//            }


            // add this, anything that's initially not in the view (on false branch) never become visible
//            Color.green

//            if flag {
//                Color.blue
//            } else {
//                Color.green
//            }

            // Add a ZStack above, this only animate the true branch, no false branch
            if flag {
                Text("👍True!")
                    .font(.system(size: 90))
                    .foregroundColor(.orange)
            } else  {
                Text("False?🥺")
                    .font(.system(size: 90))
                    .foregroundColor(.purple)
                    .padding(.top, 200)
            }


//            if flag {
//                Text("🤘True!")
//                    .font(.system(size: 90))
//                    .foregroundColor(.black)
//            }
//            if anotherFlag {
//                Text("False...🤠")
//                    .font(.system(size: 90))
//                    .foregroundColor(.orange)
//                    .padding(.top, 200)
//            }


        }
        .onAppear {
            withAnimation(Animation.linear(duration: 2).repeatForever()) {
                // calling toggle() to flip from whatever true/false initial state
                flag.toggle()
                anotherFlag.toggle()
            }
        }
    }
}

struct SimpleAnimation_Previews: PreviewProvider {
    static var previews: some View {
        SimpleAnimation()
    }
}