Persisting Color in SwiftUI

PlaygroundView.swift

//
//  PlaygroundView.swift
//  PlaygroundApp
//
//  Created by Gregor Dschung on 17.07.20.
//

import SwiftUI

struct PlaygroundView: View {
    
    @ObservedObject var viewModel: PlaygroundViewModel
    
    var body: some View {
        VStack {
            Text("Hello!")
            ColorPicker("Set background color", selection: $viewModel.color)
        }.frame(maxWidth: .infinity, maxHeight: .infinity)
        .background(viewModel.color)
        .onAppear() {
            self.viewModel.load()
        }
    }
}

class PlaygroundViewModel: ObservableObject {
    
    @Published var color: Color = Color.white {
        didSet {
            interactor.save(color: color.rgba())
        }
    }
    
    private let interactor: PlaygroundInteractor
    
    init(interactor: PlaygroundInteractor) {
        self.interactor = interactor
    }
    
    func load() {
        let previousColor = interactor.loadColor()
        color = Color(previousColor)
    }

}

// I do not think an "Interactor" should interact with UIKit or SwiftUI classes, therefore the "CoreColor".
// But of course this is a matter of taste...
class PlaygroundInteractor {
    
    private var color: CoreColor = (0.5, 0.5, 0.8, 1)
    
    func loadColor() -> CoreColor {
        // load from storage ...
        return color
    }
    
    func save(color: CoreColor) {
        print("Color to save: \(color)")
        self.color = color
    }
}

typealias CoreColor = (red: Double, green: Double, blue: Double, opacity: Double)

extension Color {
    
    init(_ rgba: CoreColor) {
        self.init(.sRGB, red: rgba.red, green: rgba.green, blue: rgba.blue, opacity: rgba.opacity)
    }
    
    func rgba() -> CoreColor {
        let uicolor = UIColor(self)
        var r: CGFloat = 0
        var g: CGFloat = 0
        var b: CGFloat = 0
        var a: CGFloat = 0
        uicolor.getRed(&r, green: &g, blue: &b, alpha: &a)
        return (red: Double(r), green: Double(r), blue: Double(b), opacity: Double(a))
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        let interactor = PlaygroundInteractor()
        let viewModel = PlaygroundViewModel(interactor: interactor)
        PlaygroundView(viewModel: viewModel)
    }
}