Article related to this project

• The Advanced Guide to UserDefaults in Swift.

UserDefaultsPropertyWrapper

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)