Code Quality Rank: L4
Programming language: Swift
License: MIT License
Latest version: v5.1.0

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Prephirences - Preϕrences

License Platform Language Issues Cocoapod Carthage compatible Build Status

Prephirences is a Swift library that provides useful protocols and convenience methods to manage application preferences, configurations and app-state.

  @Preference(key: "enabled")
  var enabled: Bool?

  @UserDefaultsPreference(key: "my.string.pref")
  var pref: String?

  @MutablePreference(preferences: UserDefaults.standard, key: "enabled")
  var enabled: Bool?
let userDefaults = UserDefaults.standard
if let enabled = userDefaults["enabled"] as? Bool {..}
userDefaults["mycolorkey", archive] = UIColor.blue

Preferences is not only UserDefaults, it could be also :

  • Keychain to store credential
  • Any dictionary
  • Application information from Bundle
  • File stored preferences (ex: plist)
  • iCloud stored preferences NSUbiquitousKeyValueStore
  • or your own private application preferences

ie. any object which implement the simple protocol PreferencesType, which define key value store methods.

You can also combine multiples preferences and work with them transparently (see Composing)




The simplest implementation of PreferencesType is DictionaryPreferences

// From Dictionary
var fromDico = DictionaryPreferences(myDictionary)
// or literal
var fromDicoLiteral: DictionaryPreferences = ["myKey": "myValue", "bool": true]

// From filepath
if let fromFile = DictionaryPreferences(filePath: "/my/file/path") {..}
// ...in main bundle ##
if let fromFile = DictionaryPreferences(filename: "prefs", ofType: "plist") {..}


You can access with all methods defined in PreferencesType protocol

if let myValue = fromDicoLiteral.object(forKey: "myKey") {..}
if let myValue = fromDicoLiteral["bool"] as? Bool {..}

var hasKey = fromDicoLiteral.hasObject(forKey: "myKey")
var myValue = fromDicoLiteral.bool(forKey: "myKey")

If you want to access using RawRepresentable enum.

enum MyKey: PreferenceKey/*String*/ {
   case Key1, Key2, ...
if let myValue = fromDicoLiteral.object(forKey: MyKey.Key1) {..}
var myValue = fromDicoLiteral.bool(forKey: MyKey.Key2)

:warning: RawRepresentableKey must be imported, see setup.


Modifiable preferences implement the protocol MutablePreferencesTypes

The simplest implementation is MutableDictionaryPreferences

var mutableFromDico: MutableDictionaryPreferences = ["myKey": "myValue"]

mutableFromDico["newKey"] = "newValue"
mutableFromDico.set("myValue", forKey: "newKey")
mutableFromDico.set(true, forKey: "newKey")

You can append dictionary or other PreferencesType using operators

mutableFromDico += ["newKey": "newValue", "otherKey": true]

You can also remove one preference

mutableFromDico -= "myKey"

Apply operators to one preference

You can extract a MutablePreference from any MutablePreferencesTypes and apply operators according to its value type

var intPref: MutablePreference<Int> = aPrefs.preference(forKey: "intKey")
var intPref: MutablePreference<Int> = aPrefs <| "intKey"

intPref += 30
intPref -= 30
intPref *= 20
intPref %= 7
intPref /= 3

switch(intPref) {
   case 1: println("one")
   case 2...10: println("not one or zero but...")
   default: println("unkwown")

var boolPref: MutablePreference<Bool> = aPrefs <| "boolKey")

boolPref &= false
boolPref |= true
boolPref != true

You can also use some methods to change value

var stringPref: MutablePreference<String> = userDefaults <| "stringKey"
stringPref.apply { value in
  return value?.uppercaseString

or transform the value type using closures

let intFromBoolPref : MutablePreference<Int> = boolPref.transform { value in
  return (value ?? false) ? 1:0

Transformation and archiving

Before storing or accessing the value, transformation could be applied, which conform to protocol PreferenceTransformation.

This allow to archive, to change type, return default value if nil and many more.

You can get and set value using subscript

userDefaults["aKey", myTransformation] = myObject

if let object = userDefaults["aKey", myTransformation] {...}

If you extract one preference, use transformation property to setup the transformation

var aPref: MutablePreference<MyObject> = userDefaults <| "aKey"
aPref.transformation = myTransformation

or you can use some utility functions to specify a default value when the stored value match a condition

public var intValueMin10: MutablePreference<Int> {
  get {
    return userDefaults.preference(forKey: "intKey")
          .whenNil(use: 100)
          .ensure(when: lessThan100, use: 100)
  set {..}


Archiving is particularly useful with NSUserDefaults because NSUserDefaults can't store all type of objects. The following functions could help by transforming the value into an other type

You can archive into Data using this two methods

userDefaults.set(objectToArchive: UIColor.blueColor(), forKey: "colorKey")
userDefaults["colorKey", .Archive] = UIColor.blueColor()

and unarchive using

if let color = userDefaults.unarchiveObject(forKey: "colorKey") as? UIColor {..}
if let color = userDefaults["colorKey", .Archive]  as? UIColor {..}

If you extract one preference, use transformation property to setup archive mode

var colorPref: MutablePreference<UIColor> = userDefaults <| "colorKey"
colorPref.transformation = TransformationKey.Archive
colorPref.value = UIColor.redColor()
if let color = colorPref.value as? UIColor {..}


You can also apply for all objects type an NSValueTransformer, to transform into JSON for instance

userDefaults["colorKey", myValueTransformerToJson] = myComplexObject

if let object = userDefaults["colorKey", myValueTransformerToJson] {...}

:warning: allowsReverseTransformation must return true

Store RawRepresentable objects

For RawRepresentable objects like enum you can use the computed attribute preferenceTransformation as transformation

enum PrefEnum: String {
    case One, Two, Three
var pref: MutablePreference<PrefEnum> = preferences <| "enumKey"
pref.transformation = PrefEnum.preferenceTransformation
pref.value = PrefEnum.Two

Some implementations


UserDefaults implement PreferencesType and can be acceded with same methods

let userDefaults = UserDefaults.standard

if let myValue = userDefaults["mykey"] as? Bool {..}

NSUserDefaults implement also MutablePreferencesType and can be modified with same methods

userDefaults["mykey"] = "myvalue"
// with type to archive
userDefaults["mykey", .Archive] = UIColor.blueColor()


All Bundle implement PreferencesType, allowing to access Info.plist file.

For instance the Bundle.main contains many useful informations about your application.

Prephirences framework come with some predefined enums described in apple documentations and defined in PropertyListKeys.swift

let bundle = Bundle.main
let applicationName = bundle[.CFBundleName] as? String


To store in iCloud, NSUbiquitousKeyValueStore implement also PreferencesType

See composing chapter to merge and synchronize iCloud preferences with other preferences.

Key Value Coding

Foundation classes

You can wrap an object respond to implicit protocol NSKeyValueCoding in KVCPreferences or MutableKVCPreferences

let kvcPref = MutableKVCPreferences(myObject)

Be sure to affect the correct object type

Swift classes

Using ReflectingPreferences you can easily access to a struct or swift class. Just add extension.

struct PreferenceStruct {
    var color: String = "red"
    var age: Int
    let enabled: Bool = true
extension PreferenceStruct: ReflectingPreferences {}

You can then use all functions from PreferencesType

var pref = PreferenceStruct(color: "red", age: 33)
if pref["color"] as? String { .. }

Core Data

You can wrap on NSManageObject in ManageObjectPreferences or MutableManageObjectPreferences

let managedPref = ManageObjectPreferences(myManagedObject)


There is many way to play with plist files

  • You can use Plist (with the useful write method)
  • You can init DictionaryPreferences or MutableDictionaryPreferences with plist file
  • You can read dictionary from plist file and use set(dictionary: on any mutable preferences


To store into keychain, use an instance of KeychainPreferences

KeychainPreferences.sharedInstance // default instance with main bundle id
var keychain = KeychainPreferences(service: "com.github.example")

then store String or Data

keychain["anUserName"] = "password-encoded"

if let pass = keychain.stringForKey("anUserName") {..}


keychain.accessibility = .AccessibleAfterFirstUnlock

Sharing Keychain items

keychain.accessGroup = "AKEY.shared"


NSCoder is partially supported (dictionary is not available)

When you implementing NSCoding you can do

init?(coder decoder: NSCoder) {
  self.intVar = decoder["intVarKey"] as? Int ?? 0
  // or self.intVar = decoder.integer(forKey: "intVar")
  self.stringVar = decoder["stringVarKey"] as? String ?? ""

func encodeWithCoder(coder: NSCoder) {
  coder["intVarKey"] = self.intVar
  coder["stringVarKey"] = self.stringVar

Custom implementations


Create a custom object that conform to PreferencesType is very easy.

extension MyCustomPreferences: PreferencesType {
    func object(forKey: String) -> Any? {
        // return an object according to key
    func dictionary() -> [String : Any] {
        // return a full dictionary of key value

Only two functions are mandatory, others are automatically mapped but can be overrided for performance or readability.

  • In the same way you can implement MutablePreferencesType with set and removeObject(forKey: methods.
  • If you structure give a list of keys instead of a full dictionary, you can instead conform to PreferencesAdapter and implement func keys() -> [String].
  • You have a collection of object with each object could define a key and a value take a look at CollectionPreferencesAdapter or see NSHTTPCookieStorage implementation.

Accessing using custom key

Instead of using string or string constants, you can use an enum to define a list of keys

First create your enum with String raw value

enum MyEnum: String {
  case MyFirstKey
  case MySecondKey

Then add a subscript for your key

extension PreferencesType {
    subscript(key: MyEnum) -> Any? {
        return self[key.rawValue]

Finally access your information

if let firstValue = bundle[.MyFirstKey] {..}

You can do the same with MutablePreferencesType

Proxying preferences with prefix

You can defined a subcategory of preferences prefixed with your own string like that

let myAppPrefs = MutableProxyPreferences(preferences: userDefaults, key: "myAppKey.")
// We have :
userDefaults["myAppKey.myKey"] == myAppPrefs["myKey"] // is true

This allow prefixing all your preferences (user defaults) with same key


Composing allow to aggregate multiples PreferencesType objects into one PreferencesType

let myPreferences = CompositePreferences([fromDico, fromFile, userDefaults])
// With array literal
let myPreferences: CompositePreferences = [fromDico, fromFile, userDefaults]

// Mutable, only first mutable will be affected
let myPreferences: MutableCompositePreferences = [fromDico, fromFile, userDefaults]

You can access or modify this composite preferences like any PreferencesType.

  1. When accessing, first preferences that define a value for a specified key will respond
  2. When modifying, first mutable preferences will be affected by default, but you can set MutableCompositePreferences attribute affectOnlyFirstMutable to false to affect all mutable preferences, allowing you for instance to duplicate preferences in iCloud

The main goal is to define read-only preferences for your app (in code or files) and some mutable preferences (like UserDefaults, NSUbiquitousKeyValueStore). You can then access to one preference value without care about the origin.

Managing preferences instances

If you want to use Prephirences into a framework or want to get a Preferences without adding dependencies between classes, you can register any PreferencesType into Prephirences

as shared instance

Prephirences.sharedInstance = myPreferences

or by providing an Hashable key

Prephirences.register(preferences: myPreferences, forKey: "myKey")
Prephirences.instances()["myKey"] = myPreferences
Prephirences.instances()[NSStringFromClass(self.dynamicType)] = currentClassPreferences

Then you can access it anywhere

if let pref = Prephirences.instance(forKey: "myKey") {..}
if let pref = Prephirences.instances()["myKey"] {..}

Remote preferences

By using remote preferences you can remotely control the behavior of your app.

If you use Alamofire, Alamofire-Prephirences will help you to load preferences from remote JSON or Plist

Encrypt your preferences

You can use framework CryptoPrephirences to encrypt/decrypt your preferences using cipher from CryptoSwift


Using Cocoapods

CocoaPods is a centralized dependency manager for Objective-C and Swift. Go here to learn more.

  1. Add the project to your Podfile.

    pod 'Prephirences'
  2. Run pod install and open the .xcworkspace file to launch Xcode.

For core data

Add pod 'Prephirences/CoreData'

For RawRepresentable key

Add pod 'Prephirences/RawRepresentableKey'

For PropertyListKeys

Add pod 'Prephirences/Keys'

Using Carthage

Carthage is a decentralized dependency manager for Objective-C and Swift.

  1. Add the project to your Cartfile.

    github "phimage/Prephirences"
  2. Run carthage update and follow the additional steps in order to add Prephirences to your project.

Using xcode project

  1. Drag Prephirences.xcodeproj to your project/workspace or open it to compile it
  2. Add the Prephirences framework to your project


By kodlian

*Note that all licence references and agreements mentioned in the Prephirences README section above are relevant to that project's source code only.