SwiftUIでUndoManagerを試してみる

ContentView.swift

import SwiftUI

struct ContentView: View {
    @ObservedObject var model = Model()

    var body: some View {
        VStack {
            Toggle("On/Off", isOn: $model.isOn)
            Spacer()
            Button("Undo") {
                model.undoManager.undo()
            }
            .disabled(!model.undoManager.canUndo)
            Button("Redo") {
                model.undoManager.redo()
            }
            .disabled(!model.undoManager.canRedo)
        }
        .padding()
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

Model.swift

import Foundation

class Model: ObservableObject {
    
    var undoManager = UndoManager()

    var isOn: Bool = false{
        willSet {
            debugPrint("willSet: \(self.isOn) -> \(newValue)")
            if self.isOn != newValue {
                objectWillChange.send()
                let v = self.isOn
                debugPrint("regist handler")
                undoManager.registerUndo(withTarget: self, handler: {
                    debugPrint("handle: \($0.isOn) -> \(v)")
                    $0.isOn = v
                })
            }
        }
        didSet {
            debugPrint("didSet: \(self.isOn)")
        }
    }
        
}