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NSURLSession
 Reloaded Yokohama iOS Developers Meeting Nov. 2016 Kaz Yoshikawa [email protected]

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URLSession Reloaded About me

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Kaz Yoshikawa • Electricwoods LLC ୅ද / Digital Lynx Systems Inc. ෭୅ද • e-mail: [email protected] • twitter: @codelynx1 • Working History • Adobe Systems (Tokyo) • Lionbridge (Tokyo) • Quark (Tokyo / Denver) • Hummingbird Communications (Mt. View, USA) • Fact International (Vancouver, Canada) • Perle Systems (Toronto, Canada), etc.

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URLSession Reloaded What do you use for downloading?

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URLSession Reloaded Downloading Options • CFNetwork • AFNetworking • Alamofire • NSOperation or GCD + NSData(contentsOf:) * • NSURLSession + NSURLSessionTask * or equivalent

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URLSession Reloaded Alamofire vs URLSession left Intentionally blank

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URLSession Reloaded URLSessionTask

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URLSession Reloaded URLSessionTask URLSessionDataTask URLSessionDownloadTask URLSessionUploadTask

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URLSession Reloaded URLSessionDataTask left Intentionally blank

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URLSession Reloaded URLSessionDownloadTask • Downloads in foreground or background • download continues while app is killed or sleeping • Callback closure is useless — if app is killed by system • Use delegate method to catch up what have been downloaded

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URLSession Reloaded Download Task Code DMBTT.Z$POUFOUT/40CKFDU 63-4FTTJPO%PXOMPBE%FMFHBUF\ GVODVSM4FTTJPO @TFTTJPO63-4FTTJPO EPXOMPBE5BTL63-4FTTJPO%PXOMPBE5BTL 
 EJE'JOJTI%PXOMPBEJOH5PMPDBUJPO63- \ TBWFPSQSPDFTTEPXOMPBEFEGJMF ^    GVODVSM4FTTJPO @TFTTJPO63-4FTTJPO UBTL63-4FTTJPO5BTL 
 EJE$PNQMFUF8JUI&SSPSFSSPS&SSPS \ FSSPSIBOEMJOH  ^ ^ MFUNZ$POUFOUT.Z$POUFOUT  MFUDPOGJHVSBUJPO63-4FTTJPO$POGJHVSBUJPOCBDLHSPVOE 
 XJUI*EFOUJGJFSNZDPOUFOUT  DPOGJHVSBUJPOBMMPXT$FMMVMBS"DDFTTGBMTF MFUTFTTJPO63-4FTTJPO DPOGJHVSBUJPODPOGJHVSBUJPO  EFMFHBUFNZ$POUFOUT EFMFHBUF2VFVFOJM  MFUUBTLTFTTJPOEPXOMPBE5BTL XJUI63- TUSJOHIUUQBQQMFDPN   UBTLSFTVNF

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URLSession Reloaded Case Study News App

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URLSession Reloaded News Type of App catalog features sports economy article article current affairs photo photo download ads ads

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URLSession Reloaded List of Contents (< 1MB) catalog features sports economy article article current affairs photo photo * * total ads ads

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URLSession Reloaded Data Task catalog features sports economy article article current affairs photo photo ads ads

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URLSession Reloaded Contents (>10MB) catalog features sports economy article article current affairs photo photo * total * ads ads

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URLSession Reloaded Download Task catalog features sports economy article article current affairs photo photo ads ads

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URLSession Reloaded Download Task catalog features sports economy article article current affairs photo photo ads ads

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URLSession Reloaded How to identify the client of downloaded binary?

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URLSession Reloaded URLSessionDownloadDelegate func urlSession(_ session: URLSession, 
 downloadTask: URLSessionDownloadTask, 
 didFinishDownloadingTo location: URL) How do I know which article or photo or ad is about this download !? Check the URL ☹ No way !!

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URLSession Reloaded URLSessionTask

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URLSession Reloaded taskIdentifier let url = URL(string: "https://www.apple.com")! let task = session.dataTask(with: url) { (data, response, error) in if let data = data { print(data as NSData) } } task.resume() task.taskIdentifier // task-id Integer • Needs keep this ID associate with article-id or other id • May be similar to use URL to identify the download owner • If you have other sessions, the ID may collide

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URLSession Reloaded taskDescription • What you want to save here? • article-id?, path to save file?, managed object ID? • But this property is just a string let url = URL(string: "https://www.apple.com")! let task = session.dataTask(with: url) { (data, response, error) in if let data = data { print(data as NSData) } } task.taskDescription = "Some useful information"
 task.resume() String

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URLSession Reloaded You underestimate the power of String..

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URLSession Reloaded Power of String JSON base64 Basically, you can put pretty much anything, but don't go too far… These are Strings as well

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URLSession Reloaded Extracting JSON from taskDescription VODVSM4FTTJPO @TFTTJPO63-4FTTJPO EPXOMPBE5BTL63-4FTTJPO%PXOMPBE5BTL  EJE'JOJTI%PXOMPBEJOH5PMPDBUJPO63- \ JGMFUEFTDSJQUJPOEPXOMPBE5BTLUBTL%FTDSJQUJPO  MFUEBUBEFTDSJQUJPOEBUB VTJOHVUG  MFUKTPOUSZ+40/4FSJBMJ[BUJPOKTPO0CKFDU XJUIEBUB PQUJPOT<> 
 BT /4%JDUJPOBSZ\ JGMFUUZQFKTPO<UZQF>BT 4USJOH\ TXJUDIUZQF\ DBTFBSUJDMF JGMFUBSUJDMF*%KTPO<BJE>BT 4USJOH  MFUQBUI5P4BWFKTPO<QBUI>BT 4USJOH\ MFUQBUI QBUI5P4BWFBT/44USJOH FYQBOEJOH5JMEF*O1BUI NPWFGJMFGSPNMPDBUJPOUPUIJTQBUI ^ DBTFBETǘ DBTFJNBHFǘ EFGBVMUCSFBL ^ ^ ^ ^

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URLSession Reloaded UIApplicationDelegate DMBTT"QQ%FMFHBUF6*3FTQPOEFS 6*"QQMJDBUJPO%FMFHBUF\ 
 GVODBQQMJDBUJPO @BQQMJDBUJPO6*"QQMJDBUJPO 
 IBOEMF&WFOUT'PS#BDLHSPVOE63-4FTTJPOJEFOUJGJFS4USJOH 
 DPNQMFUJPO)BOEMFS!FTDBQJOH 7PJE \ 
 $BMMFEXIFOUIFBQQMJDBUJP DPNQMFUJPO)BOEMFS  ^ 
 ^

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URLSession Reloaded ZDownloader https://gist.github.com/codelynx/806913e8b4122d5ea0997fad386b97a0

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URLSession Reloaded ZDownloader architecture ZDownloader ZDownloadable ZDownloaderDelegate request URLSession request delegate find find

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URLSession Reloaded ZDownloader • Should be setup at launch time • Schedule downloading • A ZDownloader for a session • delegate of URLSession • ask ZDownloaderDelegate to fetch / construct ZDownloadable • decode JSON and pass downloaded binary to ZDownloadable

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URLSession Reloaded ZDownloadDelegate • Knows how to find or create ZDownloadable from JSON

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URLSession Reloaded ZDownloadable • Represent a downloadable object • NSDictionary to represent that downloadable object uniquely • Will get called when download is completed or error

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URLSession Reloaded Sample Project Image Downloader

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URLSession Reloaded ZDownloader architecture ZDownloader ZDownloadable ZDownloaderDelegate request URLSession request delegate find find

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URLSession Reloaded ZDownloader architecture ZDownloader ZDownloadable ZDownloaderDelegate request URLSession request delegate find find

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URLSession Reloaded Sample Project

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URLSession Reloaded ZDownloaderSample

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URLSession Reloaded ZDownloaderSample • Pick 256 images from 5000 URLs randomly • Download images in background • Show downloaded images in Collection View • Tap "reload" to re-pick 256 images and download

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URLSession Reloaded Thanks