SwiftUI can not update class data updates - swiftui

Question

I came across a situation that you use class data as your data source, and display them in a swiftUI list view, when you update your data source, the swiftUI list view won't be updated, what can we do to make the class data updates interactive with swiftUI?
see code blow:
I define the environment object :
import Foundation
import Combine
class DataSource: ObservableObject {
public static let shared = DataSource()
#Published var datalist: [RowData] = []
func fetch() -> Void {
for n in 1...50 {
let data = RowData(title: "Index:\(n)", count: 0)
datalist.insert(data, at: 0)
}
}
func update() {
for data in datalist {
data.count = data.count+1
print("\(data.title) update count to :\(data.count)")
data.objectWillChange.send()
}
self.objectWillChange.send()
}
}
to display each data in a Row View:
import SwiftUI
struct RowView: View {
#State var data: RowData
var body: some View {
HStack{
Text(data.title)
Spacer()
Text("\(data.count)")
}.padding()
}
}
struct RowView_Previews: PreviewProvider {
static var previews: some View {
RowView(data: RowData(title: "text", count: 1))
}
}
class RowData: ObservableObject {
var title: String = ""
var count: Int = 0
init(title: String, count: Int) {
self.title = title
self.count = count
}
}
in content view, display the data in a list view, I would like to refresh all the view updates when click update button. the button triggers the update methods to update the class data value from data source.
struct ContentView: View {
#EnvironmentObject var data: DataSource
#State var shouldUpdate:Bool = false
#State var localData:[RowData] = []
var body: some View {
VStack {
Button(action: {
// your action here
self.data.update()
self.shouldUpdate.toggle()
self.localData.removeAll()
self.localData = self.data.datalist
}) {
Text("update")
}
List {
ForEach(0..<self.localData.count, id:\.self) { index in
RowView(data: self.localData[index])
}
}
}
}
}

Answer 1

Well... I don't see the reason to have localData, but, anyway, here is modified code that works.
Tested with Xcode 12 / iOS 14
class DataSource: ObservableObject {
public static let shared = DataSource()
#Published var datalist: [RowData] = []
func fetch() -> Void {
for n in 1...50 {
let data = RowData(title: "Index:\(n)", count: 0)
datalist.insert(data, at: 0)
}
}
func update() {
for data in datalist {
data.count = data.count+1
print("\(data.title) update count to :\(data.count)")
}
self.objectWillChange.send()
}
}
struct RowView: View {
#ObservedObject var data: RowData
var body: some View {
HStack{
Text(data.title)
Spacer()
Text("\(data.count)")
}.padding()
}
}
class RowData: ObservableObject {
#Published var title: String = ""
#Published var count: Int = 0
init(title: String, count: Int) {
self.title = title
self.count = count
}
}
struct ContentView: View {
#EnvironmentObject var data: DataSource
#State var localData:[RowData] = []
var body: some View {
VStack {
Button(action: {
// your action here
self.data.update()
self.localData = self.data.datalist
}) {
Text("update")
}
List {
ForEach(0..<self.localData.count, id:\.self) { index in
RowView(data: self.localData[index])
}
}
}
.onAppear {
self.data.fetch()
self.localData = self.data.datalist
}
}
}