In my app, I try to download a batch of images from a server.
I'm getting a number of errors, one of which I can't find an explanation for. I checked Apple's URL loading system error codes, but I couldn't fine one for error code 12. I also got HTTP load failed (error code: -999) (which is NSURLErrorCancelled) and Task finished with error - code: -1001(which is NSURLErrorTimedOut).
I recently switched from using deprecated NSURLConnection to NSURLSession. With the former, I also got the 999 and 1001 errors, but I'm trying to find out what error code 12 means.
- (void)loadImage:(LeafletURL*)leafletURLInput isThumbnail:(BOOL)isThumbnailInput isBatchDownload:(BOOL)isBatchDownload isRetina:(BOOL)isRetina
{
isRetina_ = isRetina;
if (session)
{
/*is this the right call here? */
[session invalidateAndCancel];
[session release];
session = nil;
}
if (mImageData)
{
[mImageData release];
mImageData = nil;
}
self.leafletURL = leafletURLInput;
self.isThumbnail = isThumbnailInput;
NSString* location = (self.isThumbnail) ?leafletURL.thumbnailLocation :leafletURL.hiResImageLocation;
//// Check if the image needs to be downloaded from server. If it is a batch download, then override the local resources////
if ( ([location isEqualToString:kLocationServer] || (isBatchDownload && [location isEqualToString:kLocationResource])) && self.leafletURL.rawURL != nil )
{
//NSLog(#"final loadimage called server");
//// tell the delegate to get ride of the old image while waiting. ////
if([delegate respondsToSelector:#selector(leafletImageLoaderWillBeginLoadingImage:)])
{
[delegate leafletImageLoaderWillBeginLoadingImage:self];
}
mImageData = [[NSMutableData alloc] init];
/*download tasks have their data written to a local temp file. It’s the responsibility of the completion handler to move the file from its temporary location to a permanent location.*/
NSURL* url = [NSURL URLWithString:[leafletURL pathForImageOnServerUsingThumbnail:self.isThumbnail isRetina:isRetina]];
NSURLRequest* request = [NSURLRequest requestWithURL:url];
session = [NSURLSession sharedSession];
dataTask = [session dataTaskWithRequest:request
completionHandler:^(NSData *data, NSURLResponse *response, NSError *error)
{
// do something with the data
}];
[dataTask resume];
}
//// if not, tell the delegate that the image is already cached. ////
else
{
if([delegate respondsToSelector:#selector(leafletImageLoaderDidFinishLoadingImage:)])
{
[delegate leafletImageLoaderDidFinishLoadingImage:self];
}
}
}
I submitted an app to the store which was subsequently rejected, as it connects to an external server to load a json feed, which runs on IPv4. There are two separate internet connections where I work. The app successfully loads the json feed on one of the connections, but returns a 404 not found error on the other. Obviously when the app was in review it must have returned a 404 error. I am using a NSURLSession to connect to the api, as I understand it this is able to handle IPv4 to IPv6 mapping. What other method can I use to prevent this 404 not found error? The following is a snippet of my code:
NSURLSession *session = [NSURLSession sharedSession];
NSLog(#"%#", session.configuration);
[[session dataTaskWithURL:[NSURL URLWithString:jSONURLString]
completionHandler:^(NSData *rawData,
NSURLResponse *response,
NSError *error) {
if ((rawData != nil) && (error == nil)) {
//NSLog(#"Data: %#", rawData);
//NSLog(#"%#",response);
dispatch_async(dispatch_get_main_queue(), ^{
[self performSelector:#selector(returnRawData:) withObject:rawData];
});
}
else {
NSLog(#"error...");
dispatch_async(dispatch_get_main_queue(), ^{
[self performSelector:#selector(noFeedReturned)];
});
}
// handle response
}] resume];
Solution was to reconfigure the server to be compatible with both IPv4 and IPv6
Following upgrading to Xcode 7 (7A21B) an AFNetworking error is thrown when building my current project in AFURLSessionManager.m. I've linked AFNetworking as a submodule in Git so it's regularly up to date.
The error is
AFURLSessionManager.m:288:87: Null passed to a callee that requires a non-null argument
The line responsible:
NSURLSessionDataTask *dataTask = [[NSURLSession sessionWithConfiguration:nil] dataTaskWithURL:nil];
Obviously the nil arguments need to either be replaced with values or the method to instantiate the dataTask object needs to change but I'm not familiar enough with AFNetworking to make the change myself.
This is the entire method:
+ (void)initialize {
if ([NSURLSessionTask class]) {
NSURLSessionDataTask *dataTask = [[NSURLSession sessionWithConfiguration:nil] dataTaskWithURL:nil];
Class taskClass = [dataTask superclass];
af_addMethod(taskClass, #selector(af_resume), class_getInstanceMethod(self, #selector(af_resume)));
af_addMethod(taskClass, #selector(af_suspend), class_getInstanceMethod(self, #selector(af_suspend)));
af_swizzleSelector(taskClass, #selector(resume), #selector(af_resume));
af_swizzleSelector(taskClass, #selector(suspend), #selector(af_suspend));
[dataTask cancel];
}
}
Is there a way I can quench this error?
Tree solutions. Either use the shared session:
NSURLSessionDataTask *dataTask = [[NSURLSession sharedSession] dataTaskWithURL:nil];
or decide on a configuration. Will you send files in background or only if your app is in foreground? Replace nil with either
[NSURLSessionConfiguration defaultSessionConfiguration]
or with
[NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:#"My Identifier"]
or use NSURLSession directly instead of an obsolete third party framework.
This was a simple mistake. Thanks to Quentin for highlighting that the submodule in Git had not been updated. Doing this rectified the error.
I need to get image information from server, such image name, image id. Then use image id as one of parameters to make post, get image actual data. More specific, there are three images I should get.
First, I use getImageInfo to get image information.
- (void)getImageInfo {
// compose request
NSUserDefaults *getUserInfo = [NSUserDefaults standardUserDefaults];
NSString *uid = [getUserInfo objectForKey:#"uid"];
NSString *checkCode = [getUserInfo objectForKey:#"checkCode"];
NSString *data = [NSString stringWithFormat:#"uid=%#&yangzhengma=%#", uid, checkCode];
NSURL *url = [NSURL URLWithString:#"http://121.199.35.173:8080/xihuan22dcloud/services/Shibietupianservice/serviceGetallshibietu"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
request.HTTPBody = [data dataUsingEncoding:NSUTF8StringEncoding];
request.HTTPMethod = #"POST";
[[self.session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error){
if (!error) {
NSHTTPURLResponse *httpResp = (NSHTTPURLResponse*) response;
if (httpResp.statusCode == 200) {
// parse data in ram and put into images' imageInfos array
[self.images parseImageInfo:[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]];
[self getImageRawData];
dispatch_async(dispatch_get_main_queue(), ^{
[self.tableView reloadData];
});
}
}
}] resume];}
Then I use getImageRawData to get three image data.
- (void)getImageRawData {
// compose request dynamically
NSUserDefaults *getUserInfo = [NSUserDefaults standardUserDefaults];
NSString *uid = [getUserInfo objectForKey:#"uid"];
NSString *checkCode = [getUserInfo objectForKey:#"checkCode"];
NSURL *url = [NSURL URLWithString:#"http://121.199.35.173:8080/xihuan22dcloud/services/Shibietupianservice/serviceGetthetupian"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
request.HTTPMethod = #"POST";
NSInteger count = 0;
for (ImageInformation *temp in self.images.imageInfos) {
NSString *data = [NSString stringWithFormat:#"uid=%#&yangzhengma=%#&tupianid=%#", uid, checkCode, temp.imageId];
request.HTTPBody = [data dataUsingEncoding:NSUTF8StringEncoding];[[self.session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error){
// if client side is no errors, continue
if (!error) {
// if server side is no errors, continue
NSHTTPURLResponse *httpResp = (NSHTTPURLResponse*) response;
if (httpResp.statusCode == 200) {
NSLog(#"图片内容：%#", [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]);
// in ram and put into images' imageRawData array
[self.images parseImageRawData:[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] withImageId:temp.imageId withIndex:count];
// store data to disk
// NSString *path = [[NSString alloc] initWithFormat:#"image%#", temp.imageId];
// [FCFileManager writeFileAtPath:path content:data];
dispatch_async(dispatch_get_main_queue(), ^{
[self.tableView reloadData];
});
}
}
}] resume];
count++;
}}
Here, it will loop three times, three responses come back, only the last one is complete, the others carry a error message, or incomplete raw data sometimes. Now I'm diving into concurrency programming guide, I guess serial queue likely can solve this problem.
Output like this:
2014-12-16 22:38:48.739 WeddingNewVersion[997:83366] 图片内容：<ns:serviceGetthetupianResponse xmlns:ns="http://serviceimpl.my.com"><ns:return>error</ns:return></ns:serviceGetthetupianResponse>
2014-12-16 22:38:48.749 WeddingNewVersion[997:83366] 图片内容：<ns:serviceGetthetupianResponse xmlns:ns="http://serviceimpl.my.com"><ns:return>error</ns:return></ns:serviceGetthetupianResponse>
2014-12-16 22:38:51.943 WeddingNewVersion[997:83366] 图片内容：<ns:serviceGetthetupianResponse xmlns:ns="http://serviceimpl.my.com"><ns:return>/9j/...(complete data)...9k=%%226654474.0</ns:return></ns:serviceGetthetupianResponse>
parameters of requests:
2014-12-17 14:59:25.364 WeddingNewVersion[1875:226651] uid=6&yangzhengma=odWoDXWcBv1jOrEhywkq7L&tupianid=41
2014-12-17 14:59:25.368 WeddingNewVersion[1875:226651] uid=6&yangzhengma=odWoDXWcBv1jOrEhywkq7L&tupianid=42
2014-12-17 14:59:25.368 WeddingNewVersion[1875:226651] uid=6&yangzhengma=odWoDXWcBv1jOrEhywkq7L&tupianid=43
the problem is likely not in composing request.
------------------------------------------------update1-----------------------------------------------
I have tried to put data task of session into a serial queue. Disappointed, this is not working.
dispatch_async(self.serialQueue, ^{
[[self.session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error){...}] resume];
});
Meanwhile, I make delegateQueue of session as nil, reference says if nil, the session creates a serial operation queue for performing all delegate method calls and completion handler calls.
Now I am still confused how to make it right.
-----------------------------------------------update2------------------------------------------------
I add [NSThread sleepForTimeInterval:0.5] into the block dispatched to serial queue.
dispatch_async(self.serialQueue, ^{
[[self.session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error){...}] resume];
[NSThread sleepForTimeInterval:0.5];
});
It does not work. The three responses are complete, but they are all the same.
Thank you in advance!
I'm just guessing as I've never tried it, but possibly your data tasks are all using the same TCP port on your end.
That would be OK if they were serialized - one after the other, in sequence - but if they overlap, then the server would receive garbled HTTP requests:
GET /foo
GET /bar
GET /baz
What the server would see might be something like:
GET /fGET /baroo
GET /baz
That your third requests actually works OK might be an accident of the timing.
If you absolutely require the three requests to be issued simultaneously, there are ways to open three different ports on your end. I don't know how to do it with Cocoa and Objective-C, but you can certainly do it with C and Berkeley Socket system calls. The Cocoa / Cocoa Touch networking methods are just wrappers around sockets.
A couple of thoughts:
Your technique of using a single NSMutableURLRequest instance, and repeatedly mutating it for each request (while the prior requests are still in progress) is curious.
In the spirit of thread safety, I would use a separate NSMutableURLRequest for each concurrent request. You don't want to risk having your thread issuing these requests mutate the request object while some background thread performing one of the prior requests. (See Apple's Thread Safety Summary in the Threading Programming Guide in which they point out that mutable classes are not generally thread safe.)
Having said that, the NSURLConnection documentation leaves us with the impression that this request object would be copied, mitigating this problem. I don't see this sort of assurance in the NSURLSession documentation (though I suspect it does the same thing).
I don't think this is the problem here (if this was the problem, the problem would likely be more erratic than what you report, and besides, I suspect that NSURLSession is handling this gracefully, anyway), but as a matter of good thread-safe coding habits, it would be prudent to let each concurrent request have its own NSMutableURLRequest object.
You have confirmed that the information being used in the requests looks valid.
If you wanted to take this to the next level, you might use Charles (or Wire Shark or whatever tool you prefer) to observe the actual requests as they go out. These sorts of tools are invaluable for debugging these sorts of problems.
If you observe the requests in Charles and confirm that they are valid, then this categorically eliminates client-side issues from the situation.
What is curious is that you are not receiving NSError object from dataTaskWithRequest. Nor are you receiving statusCode other than 200 from your server. That means that your requests were successfully sent to the server and received by the server.
Instead, the server is processing the request, but is having a problem fulfilling the request. This leads me to wonder about the server code, itself. I suspect that there is something in the server code that is preventing concurrent operations from taking place (e.g., locking some shared resource, such as temp file or SQL table, for the duration of the request). I would take a hard look at the server code and make sure there are no potential contention issues.
Furthermore, I would modify the server code to not simply report "error", but rather to produce a meaningful error message (e.g. system provided error messages, error codes, etc.). Your server is detecting an error, so you should have it tell you precisely what that error was.
Note, I am explicitly not advising you to make your requests run sequentially. That is inadvisable. While it might solve the immediate problem, you pay a huge performance penalty doing that, and it's not scalable. And remember, you really must handle concurrent requests gracefully, as you're likely to have multiple users of the app at some point.
I would take a hard look at the server code, adding further debugging information to the error messages in order to track down the problem.
I put request into for loop, it works. The first thought of rob about NSMutableRequest and NSURLSession seems right, I'm trying to catch the whole idea. Thanks for rob's answer. Anyway, this is code.
for (ImageInformation *temp in self.images.imageInfos) {
// compose request dynamically
NSURL *url = [NSURL URLWithString:#"http://121.199.35.173:8080/xihuan22dcloud/services/Shibietupianservice/serviceGetthetupian"];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
request.HTTPMethod = #"POST";
NSString *data = [NSString stringWithFormat:#"uid=%#&yangzhengma=%#&tupianid=%#", uid, checkCode, temp.imageId];
request.HTTPBody = [data dataUsingEncoding:NSUTF8StringEncoding];
// data task
dispatch_async(self.serialQueue, ^{
[[self.session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error){
// if client side is no errors, continue
if (!error) {
// if server side is no errors, continue
NSHTTPURLResponse *httpResp = (NSHTTPURLResponse*) response;
if (httpResp.statusCode == 200) {
// in ram and put into images' imageRawData array
[self.images parseImageRawData:[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] withImageId:temp.imageId];
// store data to disk
// [FCFileManager writeFileAtPath:path content:data];
// dispatch display image task to main
dispatch_async(dispatch_get_main_queue(), ^{
if ([self.images.imageDrawDatasDic count] == [self.images.imageInfos count]) {
[self.tableView reloadData];
}
});
}
}
}] resume];
[NSThread sleepForTimeInterval:0.5];
});
}
}
I am using AFURLSessionManager, and set the manager as a singleton instance.
- (AFURLSessionManager *)backgroundSession
{
static AFURLSessionManager *backgroundSession = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
NSURLSessionConfiguration *config = [NSURLSessionConfiguration backgroundSessionConfiguration:#"com.testBackground.BackgroundDownload.BackgroundSession1234"];
backgroundSession = [[AFURLSessionManager alloc]initWithSessionConfiguration:config];
[backgroundSession setDownloadTaskDidWriteDataBlock:^(NSURLSession *session, NSURLSessionDownloadTask *downloadTask, int64_t bytesWritten, int64_t totalBytesWritten, int64_t totalBytesExpectedToWrite){
NSLog(#"i am downloading my id = %d progress= %f",downloadTask.taskIdentifier, totalBytesWritten*1.0/totalBytesExpectedToWrite);
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
}];
[backgroundSession setDownloadTaskDidFinishDownloadingBlock:^NSURL *(NSURLSession *session, NSURLSessionDownloadTask *downloadTask, NSURL *location){
NSLog(#"download finished");
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
return location;
}];
});
return backgroundSession;
}
//assign a download task
NSURLSessionDownloadTask *task = [manager1 downloadTaskWithRequest:request progress:&progress destination:^NSURL *(NSURL *targetPath, NSURLResponse *response) {
return targetPath;
} completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error) {
NSLog("%download success");
}];
[task resume];
I found that when I switch the app to the background the download task is running but when it was finished, the system call handleEventsForBackgroundURLSession will never be called.I am feeling that I have missed some setting or options. Any idea will be useful for me, thanks a lot.
- (void)application:(UIApplication *)application handleEventsForBackgroundURLSession:(NSString *)identifier completionHandler:(void (^)())completionHandler;
You probably have figured this out already but anyway, the exact same thing has happened to me while writing some test code to play with the background transfer service APIs (without AFNetworking). The solution was simply to change the identifier string for my background session configuration. Somehow the one I was using got bugged and the system wouldn't trigger the handleEventsForBackgroundURLSession callback. And not even restarting the device fixes it... however just changing the identifier does.
My theory is that my code created multiple instances of NSURLSession with the same configuration, which Apple clearly advices against (they say in the documentation that it has an undefined behavior if you do). I was obtaining the NSURLSessionConfiguration in the view controller's viewDidLoad method without a dispatch_once block, so it's certainly plausible that that happened.
As stated by Apple:
If an iOS app is terminated by the system and relaunched, the app can use the same identifier to create a new configuration object and session and retrieve the status of transfers that were in progress at the time of termination. This behavior applies only for normal termination of the app by the system. If the user terminates the app from the multitasking screen, the system cancels all of the session’s background transfers. In addition, the system does not automatically relaunch apps that were force quit by the user. The user must explicitly relaunch the app before transfers can begin again.
Hope it helps.
Stefan