LambdaKit 0.9.0

LambdaKit 0.9.0

LangLanguage SwiftSwift
ReleasedLast Release Aug 2021
SPMSupports SPM

Maintained by Keith Smiley, Scott Berrevoets, Martin Conte Mac Donell.

LambdaKit 0.9.0

  • By
  • Martin Conte Mac Donell


Closures make code clear and readable. You can write self-contained, small snippets of code instead of having the logic spread throughout your app, Cocoa is moving slowly to a block/closure approach but there are still a lot of Cocoa libraries (such as UIKit) that don't support Closures. LambdaKit hopes to facilitate this kind of programming by removing some of the annoying - and, in some cases, impeding - limits on coding with closures.


  • iOS 8.0+
  • Xcode 7.3


CocoaPods is a dependency manager for Cocoa projects.

CocoaPods 0.36 adds supports for Swift and embedded frameworks. You can install it with the following command:

$ gem install cocoapods

To integrate LambdaKit into your Xcode project using CocoaPods, specify it in your Podfile:

source ''
platform :ios, '8.0'

pod 'LambdaKit'

Then, run the following command:

$ pod install



Closure control event handling for UIControl

let button = UIButton.buttonWithType(.System) as! UIButton
button.addEventHandler(forControlEvents: .TouchUpInside) { button in
    println("Button touched!!! \(button)")


Closure functionality for UIGestureRecognizer.

let doubleTap = UITapGestureRecognizer { gesture, state in
    println("Double tap!")
doubleTap.numberOfTapsRequired = 2


Closure support for WKWebView navigation and UI delegates.

let webView = WKWebView()

webView.didStartProvisionalNavigation = { webview in
    print("didStartProvisionalNavigation: \(webview)")

webView.didFinish = { webview in
    print("didFinish \(webview)")

webView.didFailProvisionalNavigation = { webview, error in
    print("didFailProvisionalNavigation with error \(error)")

webView.didFail = { webView, error in
    print("didFail with error \(error)")

webView.didReceiveChallenge = { webView, challenge, completion in
    completion(.useCredential, URLCredential(trust: ...))

webView.shouldPreviewElement = { webview, elementInfo in
    print("shouldPreviewElement \(webview)")
    return true


UIImagePickerController with closure callback(s).

let picker = UIImagePickerController()
picker.didCancel = { picker in
    println("DID CANCEL! \(picker)")
picker.didFinishPickingMedia = { picker, media in 
    println("Media: \(media[UIImagePickerControllerEditedImage])")
self.presentViewController(picker, animated: true, completion: nil)


Closure wrapper for key-value observation.

In Mac OS X Panther, Apple introduced an API called "key-value observing." It implements an observer pattern, where an object will notify observers of any changes in state. NSNotification is a rudimentary form of this design style; KVO, however, allows for the observation of any change in key-value state. The API for key-value observation, however, is flawed, ugly, and lengthy.

Like most of the other closure abilities in LambdaKit, observation saves and a bunch of code and a bunch of potential bugs.

WARNING: Observing using closures and cocoa observers are independant. Meaning that you shouldn't add a "traditional" observer and then remove it using this wrapper nor add a closure observer and remove it using Cocoa methods.

self.observeKeyPath("testing", options: .New | .Old) { newValue, oldValue in
    println("Property was: \(oldValue), now is: \(newValue)")


MFMailComposeViewController with closure callback.

Note that when setting a completion handler, you don't have the responsability to dismiss the view controller anymore.

let composeViewController = MFMailComposeViewController { viewController, result, type in println("Done") }


MFMessageComposeViewController with closure callback.

Note that when setting a completion handler, you don't have the responsability to dismiss the view controller anymore.

let composeViewController = MFMessageComposeViewController { viewController, result in println("Done") }
composerViewController.body = "test sms"


Closure event initialization for UIBarButtonItem.

self.navigationItem.rightBarButtonItem = UIBarButtonItem(image: image, style: .Bordered) { btn in
    println("Button touched!!!!!! \(btn)")


CADisplayLink closures implementation.

CADisplayLink.runFor(5.0) { progress in
    println("Awesome \(progress * 100)%")


Closure implementation of CLLocationManager delegate.

Note that when using startUpdatingLocation(handler) you need to use the counterpart stopUpdatingLocationHandler or you'll leak memory.


let locationManager = CLLocationManager()
locationManager.starUpdatingLocation { location in
    println("Location: \(location)")


Closure implementations for common UIActivityItemProviders.

let urlProvider = ActivityURLProvider { _, activityType in
    return URL(string: "")

let activityViewController = UIActivityViewController(activityItems: [urlProvider], applicationActivities: nil)

WARNING: You cannot use closures and set a delegate at the same time. Setting a delegate will prevent closures for being called and setting a closure will overwrite the delegate property.


Martín Conte Mac Donell @fz