UserDefaults group proof of concept

README.md

Very simple proof of concept of using App Groups for UserDefaults. I use this in all my apps to share data between a main app and its widgets.

It consists of:

• UserPreferences: Struct that interacts with UserDefaults
• PreferencesModel: Observable wrapper for UserPreferences, which is used in view-related code
• ContentView: Very simple view to display something from preferences
• MyApp: Entry point for the app, initialises preferences and adds it to the environment

Note that it uses the Observable protocol which requires iOS 17, but it works fine using ObservableObject too, which is supported in all previous versions of SwiftUI.

In app extensions (like widgets) I access these the same way, either by getting it directly from UserPreferences or PreferencesModel.

Ensure that all targets (i.e. both your app and your widget) are members of the same app group in Signing & Capabilities > App Groups.

ContentView.swift

import SwiftUI

struct ContentView: View {
  @Environment(PreferencesModel.self) var preferences
 
  var body: some View {
    Text("Salary: \(preferences.salary)")
  }
}

#Preview {
  ContentView()
}

MyApp.swift

import SwiftUI

@main
struct MyApp: App {
  @State private var preferences = PreferencesModel()

  var body: some Scene {
    WindowGroup {
      ContentView()
        .environment(preferences)     
    }
  }
}

PreferencesModel.swift

import SwiftUI

@Observable
class PreferencesModel {
  var salary = UserPreferences.salary  {
    didSet { UserPreferences.salary = self.salary }
  }
}

UserDefaults+Extension.swift

import UIKit

extension UserDefaults {
  static let group = UserDefaults(suiteName: "group.com.codakuma.moneyplease")
}

UserPreferences.swift

import Foundation

struct UserPreferences {
  
  enum Keys: String {
    case salary
  }
  
  static var salary: Int {
    get {
      guard let group = UserDefaults.group else { return 0 }
      return group.integer(forKey: Keys.salary.rawValue)
    }
    set { UserDefaults.group?.set(newValue, forKey: Keys.salary.rawValue) }
  }
}