Change to @Published var in @EnvironmentObject not reflected immediately

Question

In this specific case, when I try to change an @EnvironmentObject\'s @Published var, I find that the view is not invalidated and updated immediatel

Answer 1

In Xcode 11 GM2, If you have overridden objectWillChange, then it needs to call send() on setter of a published variable.

If you don't overridden objectWillChange, once the published variables in @EnvironmentObject or @ObservedObject change, the view should be refreshed. Since in Xcode 11 GM2 objectWillChange already has a default instance, it is no longer necessary to provide it in the ObservableObject.

Answer 2

Changing

final class UserData: NSObject, ObservableObject  {

to

final class UserData: ObservableObject  {

does fix the issue in Xcode11 Beta6. SwiftUI does seem to not handle NSObject subclasses implementing ObservableObject correctly (at least it doesn't not call it's internal willSet blocks it seems).

Answer 3

A couple of things.

• Your setup doesn't work if you move the Button into MasterView either.
• You don't have a import Combine in your code (don't worry, that alone doesn't help).

Here's the fix. I don't know if this is a bug, or just poor documentation - IIRC it states that objectWillChange is implicit.

Along with adding import Combine to your code, change your UserData to this:

final class UserData: NSObject, ObservableObject  {
    var objectWillChange = PassthroughSubject<Void, Never>()
    @Published var changeView: Bool = false {
        willSet {
            objectWillChange.send()
        }
    }
}

I tested things and it works.