Working with web APIs in Swift

Twilio Signal, May 19, 2015
https://www.youtube.com/watch?v=ISyve2_dj6c

Swift is Apple's hot new programming language for building iOS and OS X apps. This talk will demonstrate an example app in Swift that connects to the Dropbox API. We'll explore topics that apply to working with any API, including best practices for making snappy and resilient requests as well as handling JSON success and error responses.

Transcript

1. Working with web APIs in Swift Leah Culver Twilio Signal 2015
2. Dropbox Developer Platform
3. New! Dropbox API v2
4. API v2 preview • HTTP POST method • JSON in the request and response body • fewer HTTP status codes • more descriptive error messages • general cleanup ✨
5. API v2 preview endpoints User endpoints users/get_account users/get_current_account File endpoints files/get_metadata files/list_folder files/upload files/download files/search … and more!
6. New! SwiftyDropbox
7. SwiftyDropbox SDK (v0.1) methods User endpoints usersGetAccount usersGetCurrentAccount File endpoints filesGetMetadata filesListFolder filesUpload filesDownload filesSearch … and more!
8. + + + …
9. + + + ⌚
10. =
11. Photo Watch Photos from your Dropbox on your Apple Watch
12. (phone simulator)
13. github.com/dropbox/SwiftyDropbox blogs.dropbox.com/developers import SwiftyDropbox
14. Link account with Dropbox func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool { DropboxAuthManager.sharedAuthManager = DropboxAuthManager(appKey: “APP_KEY”) return true } AppDelegate.swift
15. @IBAction func linkButtonPressed(sender: AnyObject) { // Present view to log in DropboxAuthManager.sharedAuthManager.authorizeFromController(self) } ViewController.swift
16. OAuth 2 on iOS • switch to Safari for log in and authorization
17. OAuth 2 on iOS • switch to Safari for log in and authorization
18. OAuth 2 on iOS • switch to Safari for log in and authorization • present web view controller
19. OAuth 2 on iOS • switch to Safari for log in and authorization • present web view controller
20. OAuth 2 on iOS • switch to Safari for log in and authorization • present web view controller • switch to Dropbox app (“DAuth”, not yet implemented)
21. func application(application: UIApplication, openURL url: NSURL, sourceApplication: String?, annotation: AnyObject?) -> Bool { if let authResult = DropboxAuthManager.sharedAuthManager.handleRedirectURL(url) { switch authResult { case .Success(let token): println("Success! User is logged into Dropbox.") case .Error(let error, let description): println("Error: \(description)") } } return false } AppDelegate.swift
22. Set up DropboxClient // Check if the user is logged in if let token = DropboxAuthManager.sharedAuthManager.getFirstAccessToken() { // Set the sharedClient for re-use DropboxClient.sharedClient = DropboxClient(accessToken: token) … } ViewController.swift
23. List user’s Dropbox files self.filenames = [] // List contents of app folder DropboxClient.sharedClient.filesListFolder(path: "").response { response, error in if let result = response { for entry in result.entries { // Check that file is a photo (by file extension) if fileURL.absoluteString!.hasSuffix(".jpg") || fileURL.absoluteString!.hasSuffix(".png") { // Add photo self.filenames?.append(entry.name) } } } } ViewController.swift
24. UIPageViewControllerDataSource func presentationCountForPageViewController(pageViewController: UIPageViewController) -> Int // Number of pages is number of photos return self.filenames!.count }
25. UIPageViewControllerDataSource func pageViewController(pageViewController: UIPageViewController, viewControllerAfterViewController viewController: UIViewController) -> UIViewController? { var nextIndex = … let photoViewController = self.storyboard?.instantiateViewControllerWithIdentifier("PhotoViewController") as! PhotoViewController photoViewController.filename = self.filenames![nextIndex] return photoViewController }
26. Download photo class PhotoViewController: UIViewController { @IBOutlet weak var imageView: UIImageView! var filename: String? override func viewDidLoad() { … // Download the photo from Dropbox // A thumbnail would be better but there's no endpoint for that in API v2 yet! DropboxClient.sharedClient.filesDownload(path: “/\(self.filename)").response { response, error in if let (metadata, data) = response, image = UIImage(data: data) { // Resize image for watch (so it's not huge) let resizedImage = self.resizeImage(image) // Display image self.imageView.image = resizedImage } } } }
27. Cache files… share with watch…
 app group!
29. Store photos in app group // Get app group shared by phone and watch let containerURL = NSFileManager.defaultManager() .containerURLForSecurityApplicationGroupIdentifier("group.com.Dropbox.DropboxPhotoWatch") if let fileURL = containerURL?.URLByAppendingPathComponent(filename) { if let data = NSData(contentsOfURL: fileURL) { // Display image self.imageView.image = UIImage(data: data) } else { // Download the photo from Dropbox, resize, then display … self.imageView.image = resizedImage // Save image to local filesystem app group - allows us to access in the watch let resizedImageData = UIImageJPEGRepresentation(resizedImage, 1.0) resizedImageData.writeToURL(fileURL, atomically: true) } }
31. InterfaceController.swift override func awakeWithContext(context: AnyObject?) { super.awakeWithContext(context) // Get images from the shared app group if let images = self.getImagesFromAppGroup() { // Data for each photo view let controllerNames = [String](count: images.count, repeatedValue: "PhotoInterfaceController") let contexts = images.map({ image in ["image": image] }) // Update watch display WKInterfaceController.reloadRootControllersWithNames(controllerNames, contexts: contexts) } }
32. InterfaceController.swift private func getImagesFromAppGroup() -> Array<UIImage>? { var images = [UIImage]() // Get app group shared by phone and watch if let containerURL = NSFileManager.defaultManager() .containerURLForSecurityApplicationGroupIdentifier("group.com.Dropbox.DropboxPhotoWatch") { // Fetch all files in the app group for fileURL in NSFileManager.defaultManager().contentsOfDirectoryAtURL(…) as! Array <NSURL> { // Check that file is a photo (by file extension) if fileURL.absoluteString!.hasSuffix(".jpg") || fileURL.absoluteString!.hasSuffix(".png") { // Add image to array of images if let data = NSData(contentsOfURL: fileURL), image = UIImage(data: data) { images.append(image) } } } return images }
33. PhotoInterfaceController.swift class PhotoInterfaceController: WKInterfaceController { @IBOutlet weak var image: WKInterfaceImage! override func awakeWithContext(context: AnyObject?) { super.awakeWithContext(context) if let data = context as? Dictionary<String, UIImage> { self.image.setImage(data["image"]) } } }
34. (watch simulator)
35. github.com/dropbox/PhotoWatch Photo Watch
36. Working with APIs in Swift
37. let maxSize: CGFloat = 200.0 var size: CGSize? Constants and Variables
38. Optionals if let (metadata, data) = response { // … } else { println("Error: \(error!)") }
39. Optional chaining (new!) if let (metadata, data) = response, image = UIImage(data: data) { // Display image self.imageView.image = image } else { println("Error downloading file from Dropbox: \(error!)") }
40. Emoji! let = DropboxClient.sharedClient
41. HTTP requests Recommended library: NSURLSession Check out: Alamofire
42. JSON Recommended library: NSJSONSerialization Check out: ??
43. Singleton for a default - shared instance
44. iOS app longer lifetime of in-memory code Web app request/response pattern API clients DropboxClient DropboxAuthManager
45. + (id)sharedManager { static MyManager *sharedManager = nil; static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ sharedManager = [[self alloc] init]; }); return sharedManager; } class MyManager { static let sharedManager = MyManager() init() { //... } } Singletons Obj-C Swift
46. Enumerations if let authResult = DropboxAuthManager.sharedAuthManager.handleRedirectURL(url) { switch authResult { case .Success(let token): println("Success! User is logged into Dropbox.") case .Error(let error, let description): println("Error: \(description)") } }
47. public enum DropboxAuthResult { case Success(DropboxAccessToken) case Error(OAuth2Error, String) } public func handleRedirectURL(url: NSURL) -> DropboxAuthResult? { … } Enumerations
48. DropboxClient.sharedClient.filesListFolder(path: "").response { response, error in if response != nil { println(response) } else if error != nil { println("Error: \(error)") } } Completion handler
49. Feedback? leah@dropbox.com Session feedback? Text @T14 to 39242
50. Photo credits: https://www.facebook.com/media/set/?set=a.754673357914502.1073741837.669409179774254 Fox icon: http://www.funnyeve.com/ https://www.flickr.com/photos/geezaweezer/6096470743 http://www.stellamarrs.com/ https://www.flickr.com/photos/dinnerseries/14896417171 https://www.flickr.com/photos/ukgardenphotos/15826945730 https://www.flickr.com/photos/thomashawk/11708785 https://www.flickr.com/photos/kwl/7701369614