v8tr / userdefaultspropertywrapper

Swifty UserDefaults property wrapper with statically-typed keys and change observations. https://www.vadimbulavin.com/advanced-guide-to-userdefaults-in-swift/

Article related to this project

• The Advanced Guide to UserDefaults in Swift.

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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)

userdefaultspropertywrapper's Issues

UserDefaults observation not trigger

Hi ! I just stumbled across your post and tried your project since I use the same technique to observe user defaults changes in our app and it's not working anymore.

So I downloaded your project, ran it and nothing was outputted. Although I think the two lines you mention should appear:

Changed from: Optional(false) to Optional(true)
Changed from: Optional(true) to Optional(false)

I wonder if it's something general for all apps with UserDefaults. To let you know, when using a key initial when registering the observer the initial value is properly received. But that's the only one.
Have you also encountered such an issue? I would love to have your thoughts on that one.