The background color and text in ReadyDashboardView below don’t update when isConnected is updated. Obviously I want to update the view when the connection is made. I was expecting that publishing everything in the chain to that variable would make it update instantly in swiftui. Instead, it’s always rendering using the value provided when the variable is instantiated. Here’s a very simplified look at the situation:
Is there another swiftui feature i should be using or am I going to have to make some sweeping changes to my codebase?
import SwiftUI
@main
struct TestApp: App {
@StateObject private var env = PrinterEnv()
var body: some Scene {
WindowGroup {
ReadyDashboardView()
.environmentObject(env)
}
}
}
struct ReadyDashboardView: View {
@EnvironmentObject var env: PrinterEnv
var body: some View {
VStack {
HStack {
Spacer()
VStack {
Text(env.selectedPrinter?.isConnected ?? false ? "Printer Ready" : "Not Connected")
.padding(.bottom)
}
Spacer()
}
.background(env.selectedPrinter?.isConnected ?? false ? .green : .red)
Button("Connect") { env.selectedPrinter?.isConnected = true }
Button("Disconnect") { env.selectedPrinter?.isConnected = false }
}
}
}
class PrinterEnv: ObservableObject {
@Published var configuredPrinters: [Printer] = []
@Published var selectedPrinter: Printer?
init() {
configuredPrinters.append(contentsOf: [Printer()])
selectedPrinter = configuredPrinters.first
}
}
class Printer: ObservableObject {
@Published var isConnected = false
}
2
Answers
I suggest you do not nest
ObservableObject
, it does not work very well.Try a
Printer
struct for example, such as:I do not think the problem is specifically related to nested observable objects. Nesting them is working fine and is even recommended by community members as the best way to manage app wide states and ensure performance is acceptable.
See this: https://www.fivestars.blog/articles/app-state/
That said, I believe it’s probably related to the wrapping of the observable object with
@Published
property wrapper.Try this in a playground: