why is a passed parameter displaying the previous content of an EnvironmentObject - macos

Question

this is a Macos app where the parsclass is setup in a previous view that contains the YardageRowView below. That previous view is responsible for changing the contents of the parsclass. This is working is other views that use a NavigationLink to display the views.
When the parsclass is changed, this view is refreshed, but the previous value is put in the text field on the holeValueTestView.
I cannot comprehend how the value is not being passed into the holeValueTestView correctly
This is a view shown as a .sheet, and if I dismiss it and display it again, everything is fine.
if you create a macOS project called YardageSample and replace the ContentView.swift and YardageSampleApp.swift with the two files below, you can see that the display in red changes and the black numbers do not change until you click Done and redisplay the .sheet
//
// YardageSampleApp.swift
// YardageSample
//
// Created by Brian Quick on 2021-04-12.
//
import SwiftUI
#main
struct YardageSampleApp: App {
#StateObject var parsclass = parsClass()
var body: some Scene {
WindowGroup {
ContentView()
.environmentObject(parsclass)
}
}
}
//
// ContentView.swift
// YardageSample
//
// Created by Brian Quick on 2021-04-12.
//
import SwiftUI
struct ContentView: View {
#StateObject var parsclass = parsClass()
enum ActiveSheet : String , Identifiable {
case CourseMaintenance
var id: String {
return self.rawValue
}
}
#State var activeSheet : ActiveSheet? = nil
var body: some View {
Button(action: {
self.activeSheet = .CourseMaintenance
}) {
Text("Course Maintenance")
}
.sheet(item: $activeSheet) { sheet in
switch sheet {
case .CourseMaintenance:
CourseMaintenance()
}
}.frame(width: 200, height: 200, alignment: /*#START_MENU_TOKEN#*/.center/*#END_MENU_TOKEN#*/)
}
}
class parsClass: ObservableObject {
#Published var pars = [parsRec]()
init() {
self.pars = [parsRec]()
self.pars.append(parsRec())
}
func create(newpars: [parsRec]) {
pars.removeAll()
pars = newpars
}
}
class parsRec: Identifiable, Codable {
var id = UUID()
var Hole = 1
var Yardage = 1
}
struct CourseMaintenance: View {
#EnvironmentObject var parsclass: parsClass
#Environment(\.presentationMode) var presentationMode
var body: some View {
VStack {
Button(action: {presentationMode.wrappedValue.dismiss()}, label: {
Text("Done")
})
Button(action: {switchScores(number: 1)}, label: {
Text("Button 1")
})
Button(action: {switchScores(number: 2)}, label: {
Text("Button 2")
})
Button(action: {switchScores(number: 3)}, label: {
Text("Button 3")
})
CourseDetail().environmentObject(parsclass)
}.frame(width: 400, height: 400, alignment: .center)
}
func switchScores(number: Int) {
var newparRecs = [parsRec]()
for i in 0..<17 {
let myrec = parsRec()
myrec.Hole = i
myrec.Yardage = number
newparRecs.append(myrec)
}
parsclass.create(newpars: newparRecs)
}
}
struct CourseDetail: View {
#EnvironmentObject var parsclass: parsClass
var body: some View {
HStack(spacing: 0) {
ForEach(parsclass.pars.indices, id: \.self) { indice in
// this displays the previous value
holeValueTestView(value: String(parsclass.pars[indice].Yardage))
// this displays the correct value after parsclass has changed
Text(String(parsclass.pars[indice].Yardage))
.foregroundColor(.red)
}
}
}
}
struct holeValueTestView: View {
#State var value: String
var body: some View {
//TextField(String(value), text: $value)
Text(value)
}
}
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
ContentView()
}
}

Answer 1

There are a couple of issues going on:
You have multiple instances of parsClass. One is defined in YardageSampleApp and passed into the view hierarchy as a #EnvironmentObject. The second is defined in ContentView as a #StateObject. Make sure you're only using one.
On holeValueTestView, you defined value as a #State variable. That gets set initially when the view is created by its parent and then it maintains its own state. So, when the environmentObject changed, because it was in charge of its own state at this point, it didn't update the value. You can simply remove #State and see the behavior that you want.
struct ContentView: View {
#EnvironmentObject var parsclass : parsClass //<-- Here
enum ActiveSheet : String , Identifiable {
case CourseMaintenance
var id: String {
return self.rawValue
}
}
#State var activeSheet : ActiveSheet? = nil
var body: some View {
Button(action: {
self.activeSheet = .CourseMaintenance
}) {
Text("Course Maintenance")
}
.sheet(item: $activeSheet) { sheet in
switch sheet {
case .CourseMaintenance:
CourseMaintenance()
}
}.frame(width: 200, height: 200, alignment: .center)
}
}
struct holeValueTestView: View {
var value: String //<-- Here
var body: some View {
Text(value)
}
}
As a side note:
In Swift, normally type names are capitalized. If you want to write idiomatic Swift, you would change your parsClass to ParsClass for example.