【SwiftUI】Userdefaultsのエラー

前提・実現したいこと

ListのデータをUserdefaultsで保存しようと考えています。
以下のエラーを直す方法を教えていただきたいです。

発生している問題・エラーメッセージ

出ているエラーそのまま

"Attempt to insert non-property list object (\n\"pra3.Operate(id: 4C6DA55C-D1F2-4BE3-BE70-D88FB31243FA, task: \\"task\\", time: \\"60\\")\",\n    \"pra3.Operate(id: 3C743C08-2EE5-4272-8A39-C42727FEA9A6, task: \\"1\\", time: \\"1\\")\"\n) for key operate2"

要約

Attempt to insert non-property list object (~~~) for key operate2"

該当のソースコード

SwiftUI
1
2import SwiftUI
3
4struct Operate: Identifiable{
5    
6    var id = UUID()
7    var task: String
8    var time: String
9    
10    
11}
12
13var ListWidth = UIScreen.main.bounds.width
14var ListHeight = UIScreen.main.bounds.height
15
16struct OperateList: View {
17    
18    @State var pretask: String = ""
19    @State var pretime: String = ""
20    @State var operate: [Operate] = [Operate(task: "task", time: "60")]
21    
22    var body: some View {
23        
24        VStack{
25            
26            HStack{
27                
28                
29                TextField("task", text: self.$pretask).textFieldStyle(RoundedBorderTextFieldStyle()).frame(width: ListWidth / 2, height:  ListHeight / 20)
30                //taskの入力
31                
32                TextField("time", text: self.$pretime).textFieldStyle(RoundedBorderTextFieldStyle()).frame(width: ListWidth / 5, height: ListHeight / 20).keyboardType(.numberPad)
33                //timeの入力
34                
35                Button(action: {
36                    self.operate.append(Operate(task: self.pretask, time: self.pretime))
37                    self.pretask = ""
38                    self.pretime = ""
39                    UserDefaults.standard.set(self.operate, forKey: "operate2")
40                }){
41                    
42                    ZStack{
43                        RoundedRectangle(cornerRadius: 5).frame(width: ListWidth / 7, height: ListHeight / 20).foregroundColor(.green)
44                        Text("追加").foregroundColor(.white)
45                    }
46                    
47                }
48                //taskとtimeの追加
49                
50            }
51
52            
53            
54            
55            NavigationView {
56                List{
57                    
58                    ForEach(operate, id: .id){num in
59                        
60                        HStack{
61                            Text(num.task)
62                            Spacer()
63                            Text("(num.time)min")
64                        }
65                        
66                                
67                            
68                    }
69                    .onDelete(perform: delete)
70                    .onMove(perform: move)
71                    
72                    
73                }
74                .navigationBarItems(trailing: EditButton())
75                .navigationBarTitle(Text("Operate"), displayMode: .large)
76                
77            }
78            
79            
80        }.onAppear(){
81            guard let defaultItem = UserDefaults.standard.array(forKey: "operate2") as? [Operate] else{return}
82            self.operate = defaultItem
83        }
84
85        
86        
87        
88     
89    }
90    
91    
92    
93    func delete(at offsets: IndexSet){
94        operate.remove(atOffsets: offsets)
95    }
96    
97    func move(from source: IndexSet, to destination: Int){
98        operate.move(fromOffsets: source, toOffset: destination)
99    }
100    
101        
102}
103
104
105
106struct ToDoList_Previews: PreviewProvider {
107    static var previews: some View {
108        OperateList()
109    }
110    
111}
112
113
114
115