SwiftyUserDefaults

Modern Swift API for `NSUserDefaults`

SwiftyUserDefaults makes user defaults enjoyable to use by combining expressive Swifty API with the benefits of static typing. Define your keys in one place, use value types easily, and get extra safety and convenient compile-time checks for free.

Previous versions' documentation: Version 4.0.0, Version 3.0.1
Migration guides: from 4.x to 5.x, from 4.0.0-alpha.1 to 4.0.0-alpha.3, from 3.x to 4.x

Version 5.0.0

Features • Usage • Codable • NSCoding • RawRepresentable • Extending existing types • Custom types

Property wrappers • KVO • dynamicMemberLookup • Launch arguments • Utils • Installation

Features

There's only one step to start using SwiftyUserDefaults:

Define your keys!

extension DefaultsKeys {
    var username: DefaultsKey<String?> { .init("username") }
    var launchCount: DefaultsKey<Int> { .init("launchCount", defaultValue: 0) }
}

And just use it ;-)

// Get and set user defaults easily
let username = Defaults[\.username]
Defaults[\.hotkeyEnabled] = true

// Modify value types in place
Defaults[\.launchCount] += 1
Defaults[\.volume] -= 0.1
Defaults[\.strings] += "… can easily be extended!"

// Use and modify typed arrays
Defaults[\.libraries].append("SwiftyUserDefaults")
Defaults[\.libraries][0] += " 2.0"

// Easily work with custom serialized types
Defaults[\.color] = NSColor.white
Defaults[\.color]?.whiteComponent // => 1.0

If you use Swift 5.1 - good news! You can also use keyPath dynamicMemberLookup:

Defaults.color = NSColor.white

See more at the KeyPath dynamicMemberLookup section.

Usage

Define your keys

To get the most out of SwiftyUserDefaults, define your user defaults keys ahead of time:

let colorKey = DefaultsKey<String>("color", defaultValue: "")

Just create a DefaultsKey object, put the type of the value you want to store in angle brackets, the key name in parentheses, and you're good to go. If you want to have a non-optional value, just provide a defaultValue in the key (look at the example above).

You can now use the Defaults shortcut to access those values:

Defaults[key: colorKey] = "red"
Defaults[key: colorKey] // => "red", typed as String

The compiler won't let you set a wrong value type, and fetching conveniently returns String.

Take shortcuts

For extra convenience, define your keys by extending magic DefaultsKeys class and adding static properties:

extension DefaultsKeys {
    var username: DefaultsKey<String?> { .init("username") }
    var launchCount: DefaultsKey<Int> { .init("launchCount", defaultValue: 0) }
}

And use the shortcut dot syntax:

Defaults[\.username] = "joe"
Defaults[\.launchCount] += 1

Supported types

SwiftyUserDefaults supports all of the standard NSUserDefaults types, like strings, numbers, booleans, arrays and dictionaries.

Here's a full table of built-in single value defaults:

Single value	Array
`String`	`[String]`
`Int`	`[Int]`
`Double`	`[Double]`
`Bool`	`[Bool]`
`Data`	`[Data]`
`Date`	`[Date]`
`URL`	`[URL]`
`[String: Any]`	`[[String: Any]]`

But that's not all!

Codable

Since version 4, SwiftyUserDefaults support Codable! Just conform to DefaultsSerializable in your type:

final class FrogCodable: Codable, DefaultsSerializable {
    let name: String
 }

No implementation needed! By doing this you will get an option to specify an optional DefaultsKey:

let frog = DefaultsKey<FrogCodable?>("frog")

Additionally, you've got an array support for free:

let froggies = DefaultsKey<[FrogCodable]?>("froggies")

NSCoding

NSCoding was supported before version 4, but in this version we take the support on another level. No need for custom subscripts anymore! Support your custom NSCoding type the same way as with Codable support:

final class FrogSerializable: NSObject, NSCoding, DefaultsSerializable { ... }

No implementation needed as well! By doing this you will get an option to specify an optional DefaultsKey:

let frog = DefaultsKey<FrogSerializable?>("frog")

Additionally, you've got an array support also for free:

let froggies = DefaultsKey<[FrogSerializable]?>("froggies")

RawRepresentable

And the last but not least, RawRepresentable support! Again, the same situation like with NSCoding and Codable:

enum BestFroggiesEnum: String, DefaultsSerializable {
    case Andy
    case Dandy
}

No implementation needed as well! By doing this you will get an option to specify an optional DefaultsKey:

let frog = DefaultsKey<BestFroggiesEnum?>("frog")

Additionally, you've got an array support also for free:

let froggies = DefaultsKey<[BestFroggiesEnum]?>("froggies")

Extending existing types

Let's say you want to extend a support UIColor or any other type that is NSCoding, Codable or RawRepresentable. Extending it to be SwiftyUserDefaults-friendly should be as easy as:

extension UIColor: DefaultsSerializable {}

If it's not, we have two options:
a) It's a custom type that we don't know how to serialize, in this case at Custom types
b) It's a bug and it should be supported, in this case please file an issue (+ you can use custom types method as a workaround in the meantime)

Custom types

If you want to add your own custom type that we don't support yet, we've got you covered. We use DefaultsBridges of many kinds to specify how you get/set values and arrays of values. When you look at DefaultsSerializable protocol, it expects two properties in each type: _defaults and _defaultsArray, where both are of type DefaultsBridge.

For instance, this is a bridge for single value data storing/retrieving using NSKeyedArchiver/NSKeyedUnarchiver:

public struct DefaultsKeyedArchiverBridge<T>: DefaultsBridge {

    public func get(key: String, userDefaults: UserDefaults) -> T? {
        userDefaults.data(forKey: key).flatMap(NSKeyedUnarchiver.unarchiveObject) as? T
    }

    public func save(key: String, value: T?, userDefaults: UserDefaults) {
        userDefaults.set(NSKeyedArchiver.archivedData(withRootObject: value), forKey: key)
    }

    public func deserialize(_ object: Any) -> T? {
        guard let data = object as? Data else { return nil }
        return NSKeyedUnarchiver.unarchiveObject(with: data) as? T
    }    
}

Bridge for default storing/retrieving array values:

public struct DefaultsArrayBridge<T: Collection>: DefaultsBridge {
    public func save(key: String, value: T?, userDefaults: UserDefaults) {
        userDefaults.set(value, forKey: key)
    }

    public func get(key: String, userDefaults: UserDefaults) -> T? {
        userDefaults.array(forKey: key) as? T
    }

    public func deserialize(_ object: Any) -> T? {
        nil
    }
}

Now, to use these bridges in our type we simply declare it as follows:

struct FrogCustomSerializable: DefaultsSerializable {

    static var _defaults: DefaultsKeyedArchiverBridge( { DefaultsKeyedArchiverBridge() }
    static var _defaultsArray: DefaultsKeyedArchiverBridge { DefaultsKeyedArchiverBridge() }

    let name: String
}

Unfortunately, if you find yourself in a situation where you need a custom bridge, you'll probably need to write your own:

final class DefaultsFrogBridge: DefaultsBridge {
    func get(key: String, userDefaults: UserDefaults) -> FrogCustomSerializable? {
        let name = userDefaults.string(forKey: key)
        return name.map(FrogCustomSerializable.init)
    }

    func save(key: String, value: FrogCustomSerializable?, userDefaults: UserDefaults) {
        userDefaults.set(value?.name, forKey: key)
    }

    func deserialize(_ object: Any) -> FrogCustomSerializable? {
        guard let name = object as? String else { return nil }

        return FrogCustomSerializable(name: name)
    }
}

final class DefaultsFrogArrayBridge: DefaultsBridge {
    func get(key: String, userDefaults: UserDefaults) -> [FrogCustomSerializable]? {
        userDefaults.array(forKey: key)?
            .compactMap { $0 as? String }
            .map(FrogCustomSerializable.init)
    }

    func save(key: String, value: [FrogCustomSerializable]?, userDefaults: UserDefaults) {
        let values = value?.map { $0.name }
        userDefaults.set(values, forKey: key)
    }

    func deserialize(_ object: Any) -> [FrogCustomSerializable]? {
        guard let names = object as? [String] else { return nil }

        return names.map(FrogCustomSerializable.init)
    }
}

struct FrogCustomSerializable: DefaultsSerializable, Equatable {

    static var _defaults: DefaultsFrogBridge { DefaultsFrogBridge() }
    static var _defaultsArray: DefaultsFrogArrayBridge { DefaultsFrogArrayBridge() }

    let name: String
}

To support existing types with different bridges, you can extend it similarly:

extension Data: DefaultsSerializable {
    public static var _defaultsArray: DefaultsArrayBridge<[T]> { DefaultsArrayBridge() }
    public static var _defaults: DefaultsDataBridge { DefaultsDataBridge() }
}

Also, take a look at our source code (or tests) to see more examples of bridges. If you find yourself confused with all these bridges, please create an issue and we will figure something out.

Property wrappers

SwiftyUserDefaults provides property wrappers for Swift 5.1! The property wrapper, @SwiftyUserDefault, provides an option to use it with key path and options: caching or observing.

Caching means that we will store the value for you and do not hit the UserDefaults for value almost never, only for the first value fetch.

Observing means we will observe, via KVO, your property so you don't have to worry if it was saved somewhere else and you use caching.

Now usage! Given keys:

extension DefaultsKeys {
    var userColorScheme: DefaultsKey<String> { .init("userColorScheme", defaultValue: "default") }
    var userThemeName: DefaultsKey<String?> { .init("userThemeName") }
    var userLastLoginDate: DefaultsKey<Date?> { .init("userLastLoginDate") }
}

You can declare a Settings struct:

struct Settings {
    @SwiftyUserDefault(keyPath: \.userColorScheme)
    var userColorScheme: String

    @SwiftyUserDefault(keyPath: \.userThemeName, options: .cached)
    var userThemeName: String?

    @SwiftyUserDefault(keyPath: \.userLastLoginDate, options: [.cached, .observed])
    var userLastLoginDate: Date?
}

KVO

KVO is supported for all the types that are DefaultsSerializable. However, if you have a custom type, it needs to have correctly defined bridges and serialization in them.

To observe a value for local DefaultsKey:

let nameKey = DefaultsKey<String>("name", defaultValue: "")
Defaults.observe(key: nameKey) { update in
	// here you can access `oldValue`/`newValue` and few other properties
}

To observe a value for a key defined in DefaultsKeys extension:

Defaults.observe(\.nameKey) { update in
	// here you can access `oldValue`/`newValue` and few other properties
}

By default we are using [.old, .new] options for observing, but you can provide your own:

Defaults.observe(key: nameKey, options: [.initial, .old, .new]) { _ in }

KeyPath dynamicMemberLookup

SwiftyUserDefaults makes KeyPath dynamicMemberLookup usable in Swift 5.1!

extension DefaultsKeys {
    var username: DefaultsKey<String?> { .init("username") }
    var launchCount: DefaultsKey<Int> { .init("launchCount", defaultValue: 0) }
}

And just use it ;-)

// Get and set user defaults easily
let username = Defaults.username
Defaults.hotkeyEnabled = true

// Modify value types in place
Defaults.launchCount += 1
Defaults.volume -= 0.1
Defaults.strings += "… can easily be extended!"

// Use and modify typed arrays
Defaults.libraries.append("SwiftyUserDefaults")
Defaults.libraries[0] += " 2.0"

// Easily work with custom serialized types
Defaults.color = NSColor.white
Defaults.color?.whiteComponent // => 1.0

Launch arguments

Do you like to customize your app/script/tests by UserDefaults? Now it's fully supported on our side, statically typed of course.

Note: for now we support only Bool, Double, Int, String values, but if you have any other requests for that feature, please open an issue or PR and we can talk about implementing it in new versions.

You can pass your arguments in your schema:

Or you can use launch arguments in XCUIApplication:

func testExample() {
    let app = XCUIApplication()
    app.launchArguments = ["-skipLogin", "true", "-loginTries", "3", "-lastGameTime", "61.3", "-nickname", "sunshinejr"]
    app.launch()
}

Or pass them as command line arguments!

./script -skipLogin true -loginTries 3 -lastGameTime 61.3 -nickname sunshinejr

Utils

Remove all keys

To reset user defaults, use removeAll method.

Defaults.removeAll()

Shared user defaults

If you're sharing your user defaults between different apps or an app and its extensions, you can use SwiftyUserDefaults by overriding the Defaults shortcut with your own. Just add in your app:

var Defaults = DefaultsAdapter<DefaultsKeys>(defaults: UserDefaults(suiteName: "com.my.app")!, keyStore: .init())

Check key

If you want to check if we've got a value for DefaultsKey:

let hasKey = Defaults.hasKey(\.skipLogin)

Installation

Requirements

Swift version >= 4.1
iOS version >= 9.0
macOS version >= 10.11
tvOS version >= 9.0
watchOS version >= 2.0

CocoaPods

If you're using CocoaPods, just add this line to your Podfile:

pod 'SwiftyUserDefaults', '~> 5.0'

Install by running this command in your terminal:

pod install

Then import the library in all files where you use it:

import SwiftyUserDefaults

Carthage

Just add to your Cartfile:

github "sunshinejr/SwiftyUserDefaults" ~> 5.0

Swift Package Manager

Just add to your Package.swift under dependencies:

let package = Package(
    name: "MyPackage",
    products: [...],
    dependencies: [
        .package(url: "https://github.com/sunshinejr/SwiftyUserDefaults.git", .upToNextMajor(from: "5.0.0"))
    ],
    targets: [...]
)

More like this

If you like SwiftyUserDefaults, check out SwiftyTimer, which applies the same swifty approach to NSTimer.

You might also be interested in my blog posts which explain the design process behind those libraries:

Contributing

If you have comments, complaints or ideas for improvements, feel free to open an issue or a pull request.

Authors and license

Maintainer: Łukasz Mróz

Created by: Radek Pietruszewski

SwiftyUserDefaults is available under the MIT license. See the LICENSE file for more info.