urlsession reloaded
TRANSCRIPT
URLSession Reloaded
About me
Kaz Yoshikawa• Electricwoods LLC 代表 / Digital Lynx Systems Inc. 副代表
• 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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What do you use for downloading?
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Downloading Options
• CFNetwork
• AFNetworking
• Alamofire
• NSOperation or GCD + NSData(contentsOf:) *
• NSURLSession + NSURLSessionTask
* or equivalent
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Alamofire vs URLSession
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URLSessionTask
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URLSessionTask
URLSessionDataTask
URLSessionDownloadTask
URLSessionUploadTask
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URLSessionDataTask
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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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Download Task Code
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Case Study News App
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News Type of App
catalog
features
sports
economy
article
article
current affairs
photo
photo
download
adsads
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List of Contents (< 1MB)
catalog
features
sports
economy
article
article
current affairs
photo
photo
*
* total
adsads
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Data Task
catalog
features
sports
economy
article
article
current affairs
photo
photo
adsads
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Contents (>10MB)
catalog
features
sports
economy
article
article
current affairs
photo
photo
* total
*
adsads
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Download Task
catalog
features
sports
economy
article
article
current affairs
photo
photo
adsads
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Download Task
catalog
features
sports
economy
article
article
current affairs
photo
photo
adsads
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How to identify the client of downloaded binary?
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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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URLSessionTask
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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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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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You underestimate the power of String..
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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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Extracting JSON from taskDescription
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UIApplicationDelegate
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ZDownloader
https://gist.github.com/codelynx/806913e8b4122d5ea0997fad386b97a0
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ZDownloader architecture
ZDownloader ZDownloadable
ZDownloaderDelegate
request
URLSession
requestdelegate
find
find
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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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ZDownloadDelegate
• Knows how to find or create ZDownloadable from JSON
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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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Sample Project Image Downloader
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ZDownloader architecture
ZDownloader ZDownloadable
ZDownloaderDelegate
request
URLSession
requestdelegate
find
find
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ZDownloader architecture
ZDownloader ZDownloadable
ZDownloaderDelegate
request
URLSession
requestdelegate
find
find
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Sample Project
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ZDownloaderSample
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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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Thanks