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useradgents/slab 1.5.0
(iOS) Extensions to Foundation
⭐️ 4
🕓 5 weeks ago
iOS macOS tvOS
.package(url: "https://github.com/useradgents/slab.git", from: "1.5.0")


In house building, a slab is what's just over the foundations. So Slab is an overlay to Foundation, extending common types and providing convenience methods and common third-party dependencies.

It also provides two tools described in Useradgents’ iOS Architecture Guide : the Version Wizard, and the Environment Manager (with its associated Configuration Encryptor).



Slab automatically adds common dependencies to your project:

  • RNCryptor (MIT Licence) — AES encryption/decryption
  • KeychainSwift (MIT Licence) — Swifty Keychain handling
  • Reachability (MIT Licence) — Swifty replacement for Apple’s Reachability, with closures

Foundation Extensions

Array.swift, Collection.swift, Sequence.swift

  • Extension on Array:

    removing(at: Index) -> Array
            Returns a copy of the Array with the nth Element removed

    appending(_: Element) -> Array
            Returns a copy of the Array with the given Element appended         

  • Extension on Collection:

    var isNotEmpty: Bool
            A boolean value indicating the collection is not empty

  • Extension on Optional<Collection>:

    var isEmpty: Bool
            A Boolean value indicating whether the optional is nil or the wrapped collection is empty.

    var isNotEmpty: Bool
            A Boolean value indicating whether the wrappd collection is neither nil nor empty.

    var nilIfEmpty: Bool
            Collapses an empty wrapped collection into a nil

    var count: Int
            The count of the wrapped collection, or zero if the optional is nil

  • Extension on Collection<Identifiable>:

    subscript(id: Element.ID) -> Element?
            Access identifiable elements by subscripting their id         

  • Extension on Collection<Equatable>:

    replacing(_: Element, with: _Element) -> [Element]
            Returns a copy of the collection with each occurence of an element replaced with another.         

  • Extension on Collection<Collection>:

    var noneIsEmpty: Bool
            Returns true if no element in this collection is empty

    var allAreEmpty: Bool
            Returns true if all elements in this collection are empty

  • Extension on Sequence:

    sorted<T>(by: KeyPath<Element, T>, reversed: Bool = false) -> [Element]
            Returns the sequence sorted by ascending keypath, optionally reversed.


  • Provides both JSONEncoder.shared and JSONDecoder.shared (with no customization).

  • Extension on JSONDecoder:

    decode<T>(_: T.Type, at: URL) throws -> T where T : Decodable
            Decodes an instance of the indicated type from data at the given URL

  • Extension on JSONEncoder:

    encode<T>(_: T, to: URL) throws where T: Encodable
            Encodes an instance of the indicated type and writes it to the given URL

Date.swift, DateComponents.swift, DateFormatter.swift, TimeInterval.swift

Notably, these extensions allow creating DateComponents by writing


Or creating past/future Date by writing

Date.tomorrow >> 3.hours

They also implement Swift 5 string interpolation for dates: let str = "See you on \(date, using: .shortDate)"

  • New protocol

    protocol Dated
            All types adhering to this protocol have a date: Date instance variable.

  • Extension on Date:

    progress(between: Date, and: Date) -> Double
    progress(in: ClosedRange<Date>) -> Double
            Returns the fraction of time elapsed between two dates, as a Double in the range 0...1

    var dmy: DateComponents
            Returns the day, month and year components of the Date

    var isPast: Bool
    var isFuture: Bool
    var isToday: Bool
    var isTomorrow: Bool
            Returns boolean values stating whether the Date is past, future, today or tomorrow (according the current Calendar)

    var midnight: Date
        Returns a Date set to the beginning of its day (by setting hour, minute and second components to zero, according to the current Calendar)

    var timeIntervalSinceMidnight: TimeInterval
        Returns the timeInterval since midnight, according to the current Calendar.

    Getting common dates:
    static var midnight: Date
        Returns a Date set to the beginning of the current day, according to the current Calendar

    static var tomorrow: Date
        Returns a Date set to the beginning of tomorrow, according to the current Calendar

    static var yesterday: Date
        Returns a Date set to the beginning of yesterday, according to the current Calendar

    static var timeIntervalSinceMidnight: TimeInterval
        Returns the timeInterval of the beginning of the current day, according to the current Calendar

  • Extension on ClosedRange<Date>:

    var isPresent: Bool
        Returns a Bool indicating whether the Date range contains the current Date

    var isPast: Bool
    var isFuture: Bool
        Return a Bool indicating whether the Date range is entirely in the past or in the future

  • Operators:

    Date >> TimeInterval -> Date
        Adds a TimeInterval to a Date

    Date << TimeInterval -> Date
        Subtracts a TimeInterval to a Date

    Date >> DateComponents -> Date
        Adds DateComponents to a Date according to the current Calendar

    Date << DateComponents -> Date
        Subtracts DateComponents to a Date according to the current Calendar

  • Extension on Int:

    var seconds: DateComponents
    var minutes: DateComponents
    var hours: DateComponents
    var days: DateComponents
    var weeks: DateComponents
    var months: DateComponents
    var years: DateComponents
    var second: DateComponents
    var minute: DateComponents
    var hour: DateComponents
    var day: DateComponents
    var week: DateComponents
    var month: DateComponents
    var year: DateComponents
        Allow creating DateComponents by writing 1.year or 3.minutes

  • Extension on DateComponents:

    func and(_: DateComponents) -> DateComponents
        Adds other DateComponents to these DateComponents. Allows writing 1.year.and(3.months)

    var negated: DateComponents
        Negates all values of these DateComponents. Allows writing 1.year.and(1.day.negated)

    var date: Date
        Returns the Date corresponding to these DateComponents, according the the current Calendar

    var ago: Date
        Returns the current Date according to the current Calendar, minus these DateComponents. Allows writing let threeHoursAgo: Date = 3.hours.ago

    var fromNow: Date
        Returns the current Date according to the current Calendar, adding these DateComponents. Allows writing let nextYear: Date = 1.year.fromNow

    static var today: DateComponents
        Returns the day, month, year components for today

  • Extension on TimeInterval:

    var minutes: Int
    var hours: Int
        Returns the number of minutes or hours in this TimeInterval

  • Extension on DateFormatter:

    convenience init(dateFormat: String)
        Initializes a DateFormatter with the given date format

    convenience init(dateStyle: DateFormatter.Style, timeStyle: DateFormatter.Style, relative: Bool = false)
        Initializes a DateFormatter with the given date style, time style and relative flag

  • Common DateFormatters
DateFormatter. Style Example (fr_FR)
.shortDate Short date, no time 09/04/2021
.shortTime No date, short time 16:59
.relativeDate Short date, no time, relative demain
.relativeDateTime Short date, short time, relative demain 04:53
.isoDate ISO 8601 date 2021-04-09
.isoDateTime ISO 8601 date and time 2021-04-09T14:59:52+0000
.isoDateTimeMilliseconds ISO 8601 date and time (with ms) 2021-04-09T14:59:52.059Z
  • String Interpolation

    "\(Date, using: DateFormatter)"
        Example : print("See you at \(startTime, using: .shortTime)")


  • Extension on Array<Identifiable>:

    var keyedByID: [Element.ID: Element]
            Returns a dictionary where all elements of this array are keyed by their id

Numbers.swift, NumberFormatter.swift

  • String Interpolation

    "\(Int|Double|Float, using: NumberFormatter)"
        Example : print("\(percentage, using: .percent) done") with percentage = 0.25 prints "25% done"

  • Common NumberFormatters
NumberFormatter. Style Example (fr_FR)
.percentage percent style, 0 to 2 fraction digits 0.25 → "25%"
.euros currency style with EUR code 42 → "42,00 €"
.decimal decimal style, 0 to 2 fraction digits 13.3724 → "13,37"
  • Easing and interpolation

    ease(F) -> F
        sin-wave easing from [0...1] to [0...1]
        Global-scope method where F is either CGFloat, Float or Double.

    fallIn(from: ClosedRange<Self>, to: ClosedRange<Self> = 0...1) -> Self
    fallOff(from: ClosedRange<Self>, to: ClosedRange<Self> = 0...1) -> Self
        Maps value from the range inRange to outRange, rising up (fall-in) or down (fall-off). See ASCII-art comment at the top of Numbers.swift for a graphical explanation.
        Works on all instances of types conforming to FloatingPoint (CGFloat, Float, Double)    


Allows OptionSets to conform to Sequence so they become natively iterable.

struct WeekdaySet: OptionSet, Sequence {
    let rawValue: Int
    static let monday = WeekdaySet(rawValue: 1 << 0)

let weekdays: WeekdaySet = [.monday, .tuesday]
for weekday in weekdays {
    // Do something with weekday


  • Safe range formation operators

Swift will crash at runtime if creating a range from values that are not in ascending order. Slab introduces two operators .... and ...< which fix this problem.

  • Common ClosedRange<Int>:
public static var zero: ClosedRange<Int> = 0 ... 0
public static var zeroOrOne: ClosedRange<Int> = 0 ... 1
public static var any: ClosedRange<Int> = 0 ... Int.max
public static var one: ClosedRange<Int> = 1 ... 1
public static var oneOrMore: ClosedRange<Int> = 1 ... Int.max


  • Localization operator
"hello"† == NSLocalizedString("hello", comment: "?⃤ hello ?⃤")

The cross is done with alt+T on a US (QWERTY) or FR (AZERTY) keyboard. It looks like a T, so it reads like Translated

  • Extension on String:

    func matches(_ regex: String) -> Bool
            Tests if the String matches a given regular expression.

    var withoutDiacritics: String
            Returns a version of the string with diacritics removed (eg: "Älphàbêt" becomes "Alphabet").

    var initials: String
            Returns the initials of the string, by keeping the first character of each word.

    var forSort: String
            Returns a sort-friendly variant of the string (all lowercase, without diacritics).

    var cleanedUp: String
            Returns another sort-friendly variant of the string (all uppercase, without diacritics, keeping only alphanumerics).

    func sha1() -> String
            Returns the SHA-1 hash of the string.

    func sha256() -> String
            Returns the SHA-256 hash of the string.

General Tools

Custom Collections


Property Wrappers

Localise.biz fetcher

Shell script that fetches Localizable.strings and InfoPlist.strings from Localise.biz on every build.


  • Build settings accordingly to what's defined in Localise.biz.sh
  • Create a Run Script Build Phase (at the very end, after Copy Bundle Resources) named Localise.biz, with the following contents:

Version Wizard

Shell script that synchronizes build versions and numbers across multi-scheme apps, as described in Useradgents’ iOS Architecture Guide.


  • A single mandatory user-defined Build Setting must be created: VW_APP_ID, which will usually be in the form ios.<projectName>
  • Other build settings can be used to control various parts of the version wizard, they are explained directly in the VersionWizard.sh file
  • Create a Run Script Build Phase (at the very end, after Copy Bundle Resources) named Version Wizard, with the following contents:
  • Tick the checkbox so that it runs "For install builds only"

Environment Manager

Component that allows secure embedding of configuration keys, and easy runtime switching of environments.

A whole Xcode project demonstrating the Environment Manager is available in the EnvTest repository

1. Multi-scheme setup

Even though there's nothing preventing you from only using a Production environment and no other one, the Environment Manager only shines when used in a multi-scheme setup : one Production application, and one Dev application that allows runtime switching of environments.

To correctly setup your multi-scheme project, head over to Useradgents’ iOS Architecture Guide.

2. Environment Manager Setup

  • Create an Environments directory somewhere in your project
  • Add at least an env_prod.json file containing :
    "environment": {
        "name": "Production",
        "emoji": "🎢"
    "api": {
        "baseURL": "https://mywonderfulapi.io/v1/"
        [... the rest of your configuration ...]
    [... other groups of settings ...]

  • Add a "Run Script" build phase, name it "Encrypt Environments", and ensure it runs before "Copy Bundle Resources". Script contents :
  • add the Environments directory you’ve just created to the script’s Input Files, eg.
  • Build the project at least once.

  • If no failure is encountered, the file env_prod.json.aes will be created along env_prod.json. Add it to the Project Navigator.

    • Select env_prod.json, make sure it is not in the Target Membership settings (you don’t want your plain-text credentials in your final app bundle).
    • Select env_prod.json.aes and make sure it is included in the Target Membership instead.

Rinse & repeat for your other environments.

The AES files are built artifacts which are regenerated on each build, so they don’t need to be tracked. Don’t forget to add this line to your .gitignore :


3. Usage

Again, please take inspiration from the EnvTest repository which implements all of this

  • Instanciate an EnvironmentManager in your AppDelegate.

    • Production schemes don’t need no particular arguments ;
    • Development schemes must pass developmentMode: true and an optional onChange closure that will be called when the app restarts on a different environment than before (for clearing caches, disconnecting the user, …)
    • If the initializer throws an error, there’s something wrong with the setup in the previous section.
  • To retreive settings for the current environment, use:

let env = try EnvironmentManager()
let baseURL = env.url(forKey: "api.baseURL")

Other methods include string(forKey:), bool(forKey:), value(forKey:).

  • To allow selecting another environment in Development schemes, iterate over env.all which lists all the available environments as an array of Environment structs. Equality to env.current can be tested to provide a checkmark for the currently-selected environment.
  • To make another environment active, call its activate() method. This will force-sync the UserDefaults and force-quit the app with a call to exit() — which are methods that will get you a rejection from Apple if you call them in production code (even though they are not private API).
  • To easily provide environment change in SwiftUI:
struct DebugMenu: View {
    init(envManager: EnvironmentManager) {
        self.environments = envManager.allEnvironments.sorted(by: \.order)
        self.selectedEnvironment = envManager.current
    let environments: [RuntimeEnvironment]
    @State var selectedEnvironment: RuntimeEnvironment
    var body: some View {
        Form {
            Section {
                Picker("Environment", selection: $selectedEnvironment) {
                    ForEach(environments, id: \.self) {
                        Text("\($0.emoji) \($0.displayName)")
                }.onChange(of: selectedEnvironment) { environment in
                Text("Changing environment will kill the app immediately. You will need to manually launch it again.")

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