EnvironmentObject vs Singleton in SwiftUI?

Question

If the entire views access the same model in an app, I think the Singleton pattern is enough. Am I right?

For example, if MainView and ChildView access the same model(e.g. AppSetting) like below, I cannot find any reason to use EnvironmentObject instead of the Singleton pattern. Is there any problem if I use like this? If it is okay, then when I should use EnvironmentObject instead of the Singleton pattern?

class AppSetting: ObservableObject {
    static let shared = AppSetting()
    private init() {}

    @Published var userName: String = "StackOverflow"
}

struct MainView: View {
    @ObservedObject private var appSetting = AppSetting.shared

    var body: some View {
        Text(appSetting.userName)
    }
}

struct ChildView: View {
    @ObservedObject private var appSetting = AppSetting.shared

    var body: some View {
        Text(appSetting.userName)
    }
}

Thanks in advance.

The only problem is that you made it available for every type/function in your application. — Tony

Kuhlemann Kuhlemann · Accepted Answer · 2020-04-22T13:25:04

You are correct there is no reason in this case to use an EnvironmentObject. Apple even encourages to make no excessive use of EnvironmentObjects.

Nevertheless an EnvironmentObject can be great too, if you use an object in many views, because then you don't have to pass it from View A to B, from B to C and so on.

Often you find yourself in a situation where even @State and @Binding will be enough to share and update data in a view and between two views.

EnvironmentObject vs Singleton in SwiftUI?

2 Answers