I am using the NSURLsession for network calls. I need to store the details to perform the restart on network error or manually when user performs the sync from app.
Do I need to store the NSURLsession object or NSURLSessionDataTask or taskIdentifier to achieve this?
I need to initiate the restart from some other class.
Help appreciated
NSURLSession is the task, an instance of NSURLSessionTask. Three type
data tasks
upload tasks
download tasks.
You can cancel , resume these task at any point if your session still validate. If your session invalidate, You need to call that code again which start this flow.
You can see here NSURLSession
Related
I want to know about the behaviour of NSURLSessionDataTask in background.
Does NSURLSessionDataTask get paused right away (as soon as the app enters background)? or does iOS give some time hopefully 30 seconds or so until the response ?
No, You will not continue with NSURLSessionDataTask in background mode with defaultSessionConfiguration !
If you want to continue execution in background then you need to configure session with backgroundSessionConfiguration.
When you are using backgroundSessionConfiguration you can't send data directly to server, you have to give file url and from that url you have to send bytes or chunks to server, and you have to use uploadTask or downloadTask with backgroundSessionConfiguration!!
If you wants little time after entering in background then you can use UIBackgroundTaskIdentifier. These are very huge concepts to explain every thing here, It's better that you read documentations from apple or some tutorial for that!!! You should refer Apple Documentation for Background Execution and Apple documentation for NSURLSession !
I want to upload a file to a server using NSURLSession.
Cases Are:
1. It should resume uploading a file to the server from where it stopped because of app crash.
2. It should handle background upload as well.
Try AFNetworking Library to upload image asynchronously.You can find a brief example in this thread.
You should use background NSURLSession. If your app crashed or user left the app while upload was in progress, with a background NSURLSession the upload would continue seamlessly in the background. When the upload is done, your app will be notified of this via the delegate (and if your app wasn't alive at the time the download finished, it will be started in a background mode, at which point you can do whatever cleanup you need).
So create NSURLSessionConfiguration with backgroundSessionConfigurationWithIdentifier, and then instantiate a NSURLSession with that configuration.
There are a few caveats:
You cannot use completion handler pattern. You have to use delegate-based implementation.
You have to implement handleEventsForBackgroundURLSession in the app delegate, capturing the completionHandler it passes you and also instantiate the background session again. Likewise, in your NSURLSession delegate methods, you have to implement URLSessionDidFinishEventsForBackgroundURLSession, which will call the saved completion handler.
For more information, see Background Task Considerations in URL Session Programming Guide, see a section of the same name (but different text) in the NSURLSession class reference, or see the WWDC 2013 What's New in Foundation Networking, where Apple first introduced us to background sessions.
I have a situation where I need to download multiple files sequentially as each download depends on its previous downloaded file. (I am processing the file in background itself)
I am using NSURLSessionConfiguration backgroundSessionConfiguration.
There is a scenario where NSURLSessionDownloadTask initiates while the application is in background. This crashes the app with Assertion permittedbackgroundduration.
So, my question is, am I doing wrong by initiating the download task in background???
Thanks in advance,
- Satya
You have limited time when on background, so chances are that you're taking too long to process the file.
If you don't call the completion handler fast enough, the system will crash your app.
Or you may have made a mistake and you are not calling the completion handler at all on the scenario where NSURLSessionDownloadTask initiates in background.
Im trying to upload images from the Photo app through Action Extension. I use NSURLSession to upload it in background. Here is the code i use.
var configName = "com.myapp.uploadImage"
var config = NSURLSessionConfiguration.backgroundSessionConfigurationWithIdentifier(configName)
config.sharedContainerIdentifier = "group.myApp.sample"
var session = NSURLSession(configuration: config)
let task = session.dataTaskWithRequest(request)
task.resume()
self.extensionContext!.completeRequestReturningItems(self.extensionContext!.inputItems, completionHandler: nil)
It works fine.
The question is when i upload an image and dismiss the view once and then again try uploading a second image while the initial process is still running in the background, the initial NSURLSession isn't completed. Only the second process gets completed. In short, the second session overcomes the first session.
I tried using NSOperationQueue. But action extension once dismissed and opened again for the second session, it just creates a new NSOperationQueue and hence the problem still persists.
Any suggestion will be helpful. Thanks in advance.
Make sure you don't attempt to instantiate a second background session with the same identifier while the first is still running. Save your background session so you can use it later.
As the "Background Session Considerations" of the URL Loading System Programming Guide: Using NSURLSession says:
Note: You must create exactly one session per identifier (specified when you create the configuration object). The behavior of multiple sessions sharing the same identifier is undefined.
Note, this document also mentions that one "must" specify and implement the delegate. (If nothing else, how will you know about failure if you don't do that?) The example provided in the Performing Uploads and Downloads section of the App Extension Programming Guide specifies the delegate, too.
Also, has your main app's app delegate implemented the handleEventsForBackgroundURLSession method? You have to capture the completionHandler and call it when the NSURLSessionDelegate method URLSessionDidFinishEventsForBackgroundURLSession is called.
Finally, I notice that you're using data task. The NSURLSession documentation is specific that one should not be using data tasks with background sessions, only upload/download tasks. I always assumed that was just so you don't try to use didReceiveData delegate method, but I might try using upload task just in case there's some other issue associated with data tasks with background sessions.
I have a question about AFNetworking 2 and background downloads/uploads thanks to the new iOS7 NSURLSession background requests
Is this automatically handled by my AFHTTPRequestOperationManager ? Does it automatically set my requests'session to background mode?
I saw that the AFURLSessionManager Has a setDidFinishEventsForBackgroundURLSessionBlock Method but I wonder if everything is automatic?
If my app is killed or suspended, will requests keep on going? How can I get a callback when my app is relaunched?
Thanks a lot for your help!
AFHTTPRequestOperationManager uses the old NSURLConnection so that doesn't facilitate background downloading.
AFURLSessionManager uses NSURLSession under the hood so that does. I think you still need to configure the NSURLSession appropriately.
"The NSURLSession class supports background transfers while your app is suspended. Background transfers are provided only by sessions created using a background session configuration object (as returned by a call to backgroundSessionConfiguration:)."
Suggested reading:URL Loading System