Xcode on change not triggering-CodePudding

I have a custom preferences class and I would like to trigger a function whenever that is changed, at the moment it doesn't seem to work for some reason.

Here is the class

class Preferences: ObservableObject, Equatable{
static func == (lhs: Preferences, rhs: Preferences) -> Bool {
    return lhs.email == rhs.email && lhs.password == rhs.password && lhs.faceID == rhs.faceID && lhs.currency == rhs.currency && lhs.colourScheme == rhs.colourScheme && lhs.appTheme == rhs.appTheme
}

@Published var email: String = ""
@Published var password: String = ""

@Published var faceID: Bool = false

@Published var currency: Currencies = .EUR
@Published var colourScheme: ColourScheme = .system
@Published var appTheme: Theme = .orange

This is stored in a viewmodel

class ViewModel: ObservableObject {
    @Published var preferences = Preferences()
}

And here is the onchange call

        .onChange(of: viewModel.preferences){ newValue in
        viewModel.updateSettings(faceID: viewModel.preferences.faceID, currency: viewModel.preferences.currency, colourScheme: viewModel.preferences.colourScheme, appTheme: viewModel.preferences.appTheme)
    }

The onchange never gets called? Any help would be appreciated. Thanks

CodePudding user response：

Because preferences is an object there is no change, i.e. it is always the same object. SwiftUI is designed to work with value semantics, i.e. structs, so try making Preferences a struct instead.

Also there is no need for that view model object, in SwiftUI the View struct is a view model already, which SwiftUI uses to create/update/remove UIView objects on screen. We use @StateObject when we need a reference type in @State, e.g. when doing something async, however the new .task replaces that need.