A sample project showing how to implement a UserDefaults property wrapper in Swift. The property wrapper has statically typed keys and provides a conveniece to observe UserDefaults changes.
Usage:
// Declare a new key
extension Key {
static let isFirstLaunch: Key = "isFirstLaunch"
}
struct Storage {
// Use the property wrapper to add new value to `UserDefaults`
@UserDefault(key: .isFirstLaunch)
var isFirstLaunch: Bool?
}
// Initialize the storage
var storage = Storage()
// Observe user default changes
var observation = storage.$isFirstLaunch.observe { old, new in
print("Changed from: \(old) to \(new)")
}
// Make some changes
storage.isFirstLaunch = true
storage.isFirstLaunch?.toggle()It will print:
Changed from: Optional(false) to Optional(true)
Changed from: Optional(true) to Optional(false)