This application is modifying the autolayout engine from a background thread in objective c

Question

I am getting weird crash in the my application.

Mainviewcontroller.m : there is one method which call the webservice method (which is in another delegate class) and then when the response is receive the method is getting call back.

-(IBAction)signupclick:(id)sender{
     webservice_obj=[[Webservice alloc] init];
    [webservice_obj setDelegate:self];
    [webservice_obj Init_withurl:@"register" withparameter:data];
}
-(void)getresponse:(NSMutableDictionary *)response_dictionary{
    NSLog(@"dictionary==>%@",response_dictionary);
    AppDelegate *appDelegate =(AppDelegate*)[[UIApplication sharedApplication]delegate];
    [appDelegate.window setRootViewController:appDelegate.frostedViewController];
}

Delegate class : Webservice.m

-(void)Init_withurl:(NSString *)name withparameter:(NSMutableDictionary *)reqparameter{

    __block NSMutableDictionary *res_dictionary;
    NSError *error;
    NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
    NSURLSession *session = [NSURLSession sessionWithConfiguration:configuration delegate:self delegateQueue:nil];




    NSURL *url = [NSURL URLWithString:@"http://XXXXXXX"];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url
                                                           cachePolicy:NSURLRequestUseProtocolCachePolicy
                                                       timeoutInterval:60.0];

    [request addValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
    [request addValue:@"application/json" forHTTPHeaderField:@"Accept"];

    [request setHTTPMethod:@"PUT"];
     NSData *postData = [NSJSONSerialization dataWithJSONObject:reqparameter options:0 error:&error];

     [request setHTTPBody:postData];
      NSURLSessionDataTask *postDataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
        res_dictionary = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];



          [self fetchresponse:res_dictionary];



    }];

    [postDataTask resume];

}

-(void)fetchresponse:(NSMutableDictionary*)response{
    [[self delegate] getresponse:response];
}

When i execute I am getting error when below code get called in getresponse method:

 AppDelegate *appDelegate =(AppDelegate*)[[UIApplication sharedApplication]delegate];
    [appDelegate.window setRootViewController:appDelegate.frostedViewController];

Detail of the error are :

This application thread, which will cause Stack:( 0 CoreFoundation 1 libobjc.A.dylib 2 CoreFoundation 3 Foundation 4 Foundation 5 UIKit 6 UIKit 7 UIKit 8 UIKit 9 UIKit 10 UIKit 11 UIKit 12 UIKit 13 UIKit 14 UIKit 15 UIKit 16 QuartzCore 17 QuartzCore 18 QuartzCore 19 QuartzCore 20 QuartzCore 21 QuartzCore 22 libsystem_pthread.dylib 23 libsystem_pthread.dylib 24 libsystem_pthread.dylib 25 libsystem_pthread.dylib ) is modifying the autolayout engine from a background can lead to engine corruption and weird crashes. This an exception in a future release. 0x00000001127ece65 __exceptionPreprocess + 165 0x0000000112263deb objc_exception_throw + 48 0x00000001127ecd9d +[NSException raise:format:] + 205 0x0000000110504285 _AssertAutolayoutOnMainThreadOnly + 79 0x0000000110364c1e -[NSISEngine withBehaviors:performModifications:] + 31 0x00000001111aa1ca -[UIView(AdditionalLayoutSupport) _withAutomaticEngineOptimizationDisabledIfEngineExists:] + 58 0x00000001111a9b66 __57-[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:]_block_invoke + 646 0x00000001111aa1d3 -[UIView(AdditionalLayoutSupport) _withAutomaticEngineOptimizationDisabledIfEngineExists:] + 67 0x00000001111a989b -[UIView(AdditionalLayoutSupport) _switchToLayoutEngine:] + 242 0x000000011119ae6b -[UIWindow(UIConstraintBasedLayout) _switchToLayoutEngine:] + 81 0x000000011119af99 -[UIWindow(UIConstraintBasedLayout) _initializeLayoutEngine] + 282 0x000000011119b022 -[UIWindow(UIConstraintBasedLayout) _layoutEngineCreateIfNecessary] + 62 0x000000011119b2e3 -[UIWindow(UIConstraintBasedLayout) updateConstraintsIfNeeded] + 60 0x00000001111aba22 -[UIView(AdditionalLayoutSupport) _updateConstraintsAtEngineLevelIfNeeded] + 272 0x000000011098259e -[UIView(Hierarchy) _updateConstraintsAsNecessaryAndApplyLayoutFromEngine] + 159 0x00000001109924cc -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 744 0x000000010fc3259a -[CALayer layoutSublayers] + 146 0x000000010fc26e70 _ZN2CA5Layer16layout_if_neededEPNS_11TransactionE + 366 0x000000010fc26cee _ZN2CA5Layer28layout_and_display_if_neededEPNS_11TransactionE + 24 0x000000010fc1b475 _ZN2CA7Context18commit_transactionEPNS_11TransactionE + 277 0x000000010fc48c0a _ZN2CA11Transaction6commitEv + 486 0x000000010fc48efc _ZN2CA11Transaction14release_threadEPv + 224 0x0000000112ff339c _pthread_tsd_cleanup + 470 0x0000000112ff2f78 _pthread_exit + 117 0x0000000112ff1596 pthread_attr_getschedpolicy + 0 0x0000000112fef375 start_wqthread + 13

Please help and advice the standard way to call the API and do the callback and how to solve this error.

P.s : I dont want to use AFNetowrking

In `-(void)getresponse:(NSMutableDictionary *)response_dictionary`, check if you are in main thread. If not, it's the issue. You can change UI only in main thread. Use GCD (plenty of example) on how to do it in main thread. — Larme, May 02 '16 at 11:59
http://stackoverflow.com/questions/28302019/getting-a-this-application-is-modifying-the-autolayout-engine-error — Bhavin Bhadani, May 02 '16 at 11:59
@Larme thank you for the reply. But how can i navigate to main thread from the background thread ? — iOS developer, May 02 '16 at 12:00

score 1 · Accepted Answer · answered May 02 '16 at 12:13

Your crash log says that,

This application is modifying the autolayout engine from a background thread, which can lead to engine corruption and weird crashes. This will cause an exception in a future release.

So you should perform this task(modifying auto layout engine) on main thread like,

   dispatch_async(dispatch_get_main_queue(), ^{

    AppDelegate *appDelegate =(AppDelegate*)[[UIApplication sharedApplication]delegate];
    [appDelegate.window setRootViewController:appDelegate.frostedViewController];

});

Hope this will help :)

This application is modifying the autolayout engine from a background thread in objective c

1 Answers1