Background Uploading Task - ios

Question

I have been stucked in this from last week. But I did not get the solution.
I want to access all photos from camera roll and want to save all photos on remote server with the help of NSURLSessionUploadTask. For this I am using following code:
NSString *boundary = #"----WebKitFormBoundarycC4YiaUFwM44F6rT";
NSMutableData *body = [NSMutableData data];
[body appendData:[[NSString stringWithFormat:#"--%#\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"Content-Disposition: form-data; name=\"%#\"; filename=\"%#.jpeg\"\r\n", #"upload",self.pictureName] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[#"Content-Type: image/jpeg\r\n\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:self.imageData];
[body appendData:[[NSString stringWithFormat:#"\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];
[body appendData:[[NSString stringWithFormat:#"--%#--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];
config.HTTPMaximumConnectionsPerHost = 1;
config.HTTPAdditionalHeaders = #{
#"api-key" : #"55e76dc4bbae25b066cb",
#"Accept" : #"application/json",
#"Content-Type" : [NSString stringWithFormat:#"multipart/form-data; boundary=%#", boundary]
};
NSURLSession *upLoadSession = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:nil];
NSURL *url = self.uploadURL;
NSLog(#"URL=%#",url);
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
[request setHTTPMethod:#"PUT"];
[request setHTTPBody:body];
// 3
self.uploadTask = [upLoadSession uploadTaskWithRequest:request fromData:nil];
// self.uploadTask = [upLoadSession uploadTaskWithRequest:request fromFile:tmpFileUrl];
[[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES];
// 5
[_uploadTask resume];
All thing is working fine in foreground. But as I enter in background, It stop working. Where is the problem?
What I will have to do for uploading images in background using NSURLSessionUploadTask?

Answer 1

Your session config is not specified to run in the background.
NSURLSessionConfiguration *config = [NSURLSessionConfiguration backgroundSessionConfiguration:#"com.test.backgroundSession"];
NSURLSession *upLoadSession = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:nil];
Implement as above.

Answer 2

For upload task to work in background, you have to use uploadTaskWithRequest:fromFile: instead of uploadTaskWithRequest:fromData:
If you use NSData to supply the files, it will work while the app is active and will stop once the app is in background.