Stored for Swift

or, "UserDefaults Made Easy"

A simple interface for UserDefaults that allows for observing and reacting to changes to the value.
Compatible with SwiftUI.

The Problem

Writing the UserDefaults key string once, and only once, is valuable.
- Enums felt like a hack.
Out-of-sync toggles if the logic was done outside of SwiftUI
Access across the app.
- @AppStorage worked well only within the confines of the SwiftUI sphere.

The Solution

Supports Binding to SwiftUI elements.
Supports onChange() execution.
Works like it should ^TM.

Import

import Stored

Examples

Example 1. Most simple usage, storing in UserDefaults.standard by default.

// Implementation
final class LocalStorage: ObservableObject {

  @Stored("hapticFeedbackEnabled") static var hapticsEnabled: Bool = false

}

// Utilization
// The "static var" allows us to use this as a singleton value.
LocalStorage.hapticsEnabled = true

Example 2. Most elaborate usage. Stores in a custom UserDefaults, and runs a custom function when a change in value is detected.

// Implementation
final class LocalStorage: ObservableObject {

  private static var syncService: UserDefaults { UserDefaults(suiteName: "syncServicePrefs")! }

  @Stored("syncEnable", storage: LocalStorage.syncService, onChange: { _, newValue in
    
    // Observe the change.
    print("Sync \(value ? "enabled" : "disabled").")
    
    // Act upon the change.
    if newValue == true {
      synchronize()
      // ...
    }
    
  }) static var sync: Bool = false
  
}

// Utilization in a practical use case.
struct SettingsView: View {

  @AppStorage(syncService.$sync) var sync: Bool = false

  var body: some View {
    Toggle(isOn: LocalStorage.$sync) { Text("Synchronize Data") }
  }
}

// Alternate utilization. The onChange() function will fire when this runs.
UserDefaults(syncServicePrefs)?.set(true, forKey: "syncEnable")

Example 3. An alternate method of initializing a propertyWrapper that may feel more familiar.

// Implementation
final class LocalStorage: ObservableObject {

  var mark: Stored<Bool> = Stored(true, key: "mark", storage: .standard, onChange: {_,_ in })
  
}

Notes

The onChange only triggers on a successful change, not just an attempted one.

final class LocalStorage: ObservableObject {
  @Stored("mark", onChange: { _, value in
    print("result: \(value)")
  }) static var mark: Bool = false
}

UserDefaults.standard.set(false, forKey: "mark")
UserDefaults.standard.set(false, forKey: "mark")
UserDefaults.standard.set(true, forKey: "mark")

// (nothing happens)
// (nothing happens)
// result: true