Only run on the main thread exception - ios

Question

I am tracking crashes in my app. This particular crash gives me the error "Terminating app due to an uncaught exception 'NSInternalInconsistencyException', reason: 'Only run on the main thread!'". The weird thing is i can't seem to recreate the crash using my device or simulator but in my analytics it shows that this crash happens a lot. I was told this was happening because you can only do UI updates on the main thread so i updated my code but this crash keeps happening and i still can't recreate the crash on my phone or simulator.
This is code where the crash is happening:
indicator.startAnimation()
let audioData = NSData(contentsOfURL: EditSongViewController.url.urlComplete!)
let dataImage: NSData = UIImageJPEGRepresentation(songImage.image!, 1.0)!
let imageFile = PFFile(name: "photo.jpg", data: dataImage)
let audioFile = PFFile(name: "song.mp4", data: audioData)
audioFile.saveInBackground()
imageFile.saveInBackground()
let testObject = PFObject(className: "PrivateSongs")
testObject["songFile"] = audioFile
testObject["image"] = imageFile
testObject["username"] = PFUser.currentUser().username
testObject["user"] = PFUser.currentUser()
testObject["title"] = self.songTitleText.text
testObject["songInfo"] = self.songInfoText.text
if RecordViewController.fileURL.songLyrics != nil {
testObject["lyrics"] = RecordViewController.fileURL.songLyrics
}
if (isPrivate == true) {
testObject["isPrivate"] = true
} else {
testObject["isPrivate"] = false
}
testObject.saveInBackgroundWithBlock ({ (success, error) -> Void in
if (success) {
if self.chartsSwitch.on {
let chart = PFObject(className: "Songs")
chart["artistName"] = PFUser.currentUser().username
chart["songFile"] = audioFile
chart["title"] = self.songTitleText.text
chart["picture"] = imageFile
chart["user"] = PFUser.currentUser()
chart["likes"] = 0
if RecordViewController.fileURL.songLyrics != nil {
chart["lyrics"] = RecordViewController.fileURL.songLyrics
}
chart.saveInBackground()
}
PostViewControler.share.shareUrl = audioFile.url!
dispatch_async(dispatch_get_main_queue(), ^{
/* Your UI code */
self.postButton.hidden = true
self.addPictureButton.hidden = true
self.indicator.stopAnimation(false, completion: nil)
self.navigationController!.pushViewController(self.storyboard!.instantiateViewControllerWithIdentifier("ShareViewController") , animated: true)
});
} else {
dispatch_async(dispatch_get_main_queue(), ^{
/* Your UI code */
self.indicator.stopAnimation(false, completion: nil)
self.helper.showErrorAlert("Couldn't save your song please try again.")
});
}
})
Crash:
Terminating app due to an uncaught exception 'NSInternalInconsistencyException', reason: 'Only run on the main thread!' Error symbolicating crash report.
Last Exception Backtrace
0 CoreFoundation 0x2409068b
1 libobjc.A.dylib 0x3558ee17 objc_exception_throw + 38
2 CoreFoundation 0x24090561 <redacted> + 0
3 Foundation 0x24e1b0e3 <redacted> + 86
4 UIFoundation 0x323d5a6f <redacted> + 398
5 UIFoundation 0x323d57b3 <redacted> + 1510
6 UIFoundation 0x32404989 <redacted> + 724
7 UIFoundation 0x32404a7d <redacted> + 52
8 UIFoundation 0x324277a3 <redacted> + 122
9 UIFoundation 0x32427339 <redacted> + 400
10 UIFoundation 0x32426f2b <redacted> + 78
11 UIKit 0x28203227 <redacted> + 262
12 UIKit 0x28203107 <redacted> + 178
13 meipmusic 0x145e74 meipmusic + 437876
14 meipmusic 0x146e20 meipmusic + 441888
15 meipmusic 0x147144 meipmusic + 442692
16 meipmusic 0x13c994 meipmusic + 399764
17 meipmusic 0x14d760 meipmusic + 468832
18 meipmusic 0x19d810 meipmusic + 796688
19 AVFoundation 0x228625e7 <redacted> + 558
20 libdispatch.dylib 0x35c90d2b <redacted> + 10
21 libdispatch.dylib 0x35c9d92b <redacted> + 1758
22 libdispatch.dylib 0x35c9cf69 <redacted> + 284
23 libdispatch.dylib 0x35c9f665 <redacted> + 396
24 libdispatch.dylib 0x35c9f4d5 <redacted> + 96
25 libsystem_pthread.dylib 0x35e4ab45 _pthread_wqthread + 1024
26 libsystem_pthread.dylib 0x35e4a734 start_wqthread + 8
Crashed Thread 20 :
0 CoreFoundation 0x240909c7
1 libobjc.A.dylib 0x3558f09f
2 libc++abi.dylib 0x34c63e17
3 libc++abi.dylib 0x34c638f9
4 libobjc.A.dylib 0x3558ef5f
5 AVFoundation 0x22862651
6 libdispatch.dylib 0x35c90d2b <redacted> + 10
7 libdispatch.dylib 0x35c9d92b <redacted> + 1758
8 libdispatch.dylib 0x35c9cf69 <redacted> + 284
9 libdispatch.dylib 0x35c9f665 <redacted> + 396
10 libdispatch.dylib 0x35c9f4d5 <redacted> + 96
11 libsystem_pthread.dylib 0x35e4ab45 _pthread_wqthread + 1024
12 libsystem_pthread.dylib 0x35e4a734 start_wqthread + 8
Thread 0 :
0 libsystem_kernel.dylib 0x35d96164
1 CoreFoundation 0x24053905
2 CoreFoundation 0x24051c8d
3 CoreFoundation 0x23fa5249
4 CoreFoundation 0x23fa5035
5 GraphicsServices 0x2d058ad1
6 UIKit 0x281ba899
7 meipmusic 0x1849f0
8 libdyld.dylib 0x35cda873
Thread 1 :
0 libsystem_kernel.dylib 0x35dab3c0
1 libdispatch.dylib 0x35ca4f27
Thread 2 (AXSpeech):
0 libsystem_kernel.dylib 0x35d96164
1 CoreFoundation 0x24053905
2 CoreFoundation 0x24051c8d
3 CoreFoundation 0x23fa5249
4 CoreFoundation 0x23fa5035
5 Foundation 0x24d8f975
6 libAXSpeechManager.dylib 0x34694791
7 Foundation 0x24e60635
8 libsystem_pthread.dylib 0x35e4c873
9 libsystem_pthread.dylib 0x35e4c7e7
10 libsystem_pthread.dylib 0x35e4a740
Thread 3 (AVAudioSession Notify Thread):
0 libsystem_kernel.dylib 0x35d96164
1 CoreFoundation 0x24053905
2 CoreFoundation 0x24051c8d
3 CoreFoundation 0x23fa5249
4 CoreFoundation 0x23fa5035
5 libAVFAudio.dylib 0x2298a16d
6 libAVFAudio.dylib 0x2295ec87
7 libsystem_pthread.dylib 0x35e4c873
8 libsystem_pthread.dylib 0x35e4c7e7
9 libsystem_pthread.dylib 0x35e4a740
Thread 4 :
0 libsystem_kernel.dylib 0x35d96164
1 CoreFoundation 0x24053905
2 CoreFoundation 0x24051c8d
3 CoreFoundation 0x23fa5249
4 CoreFoundation 0x23fa5035
5 Foundation 0x24d8f975
6 Foundation 0x24dde58d
7 libdispatch.dylib 0x35c90d2b <redacted> + 10
8 libdispatch.dylib 0x35c9b535
9 libdispatch.dylib 0x35c9faf1
10 libdispatch.dylib 0x35c9f4d5 <redacted> + 96
11 libsystem_pthread.dylib 0x35e4ab45 _pthread_wqthread + 1024
12 libsystem_pthread.dylib 0x35e4a734 start_wqthread + 8
Thread 5 :
0 libsystem_kernel.dylib 0x35da9a60
1 libsystem_pthread.dylib 0x35e4ccb1
2 Foundation 0x24ddac27
3 meipmusic 0x41b6bb
4 Foundation 0x24e60635
5 libsystem_pthread.dylib 0x35e4c873
6 libsystem_pthread.dylib 0x35e4c7e7
7 libsystem_pthread.dylib 0x35e4a740
Thread 6 (com.apple.NSURLConnectionLoader):
0 libsystem_kernel.dylib 0x35d96164
1 CoreFoundation 0x24053905
2 CoreFoundation 0x24051c8d
3 CoreFoundation 0x23fa5249
4 CoreFoundation 0x23fa5035
5 CFNetwork 0x23917ee7
6 Foundation 0x24e60635
7 libsystem_pthread.dylib 0x35e4c873
8 libsystem_pthread.dylib 0x35e4c7e7
9 libsystem_pthread.dylib 0x35e4a740
Thread 7 (PF_AFNetworking):
0 libsystem_kernel.dylib 0x35d96164
1 CoreFoundation 0x24053905
2 CoreFoundation 0x24051c8d
3 CoreFoundation 0x23fa5249
4 CoreFoundation 0x23fa5035
5 Foundation 0x24d8f975
6 Foundation 0x24dde58d
7 meipmusic 0x4495c3
8 Foundation 0x24e60635
9 libsystem_pthread.dylib 0x35e4c873
10 libsystem_pthread.dylib 0x35e4c7e7
11 libsystem_pthread.dylib 0x35e4a740
Thread 8 (com.apple.CFSocket.private):
0 libsystem_kernel.dylib 0x35da9fb4
1 libsystem_pthread.dylib 0x35e4c873
2 libsystem_pthread.dylib 0x35e4c7e7
3 libsystem_pthread.dylib 0x35e4a740
Thread 9 (WebThread):
0 libsystem_kernel.dylib 0x35d96164
1 CoreFoundation 0x24053905
2 CoreFoundation 0x24051c8d
3 CoreFoundation 0x23fa5249
4 CoreFoundation 0x23fa5035
5 WebCore 0x32e7f287
6 libsystem_pthread.dylib 0x35e4c873
7 libsystem_pthread.dylib 0x35e4c7e7
8 libsystem_pthread.dylib 0x35e4a740
Thread 10 (JavaScriptCore::Marking):
0 libsystem_kernel.dylib 0x35da9a60
1 libsystem_pthread.dylib 0x35e4ccb1
2 libc++.1.dylib 0x34c0786d
3 JavaScriptCore 0x2565c0f5
4 JavaScriptCore 0x2565c15f
5 JavaScriptCore 0x2546dd51
6 JavaScriptCore 0x2546dcaf
7 libsystem_pthread.dylib 0x35e4c873
8 libsystem_pthread.dylib 0x35e4c7e7
9 libsystem_pthread.dylib 0x35e4a740
Thread 11 (WebCore: CFNetwork Loader):
0 libsystem_kernel.dylib 0x35d96164
1 CoreFoundation 0x24053905
2 CoreFoundation 0x24051c8d
3 CoreFoundation 0x23fa5249
4 CoreFoundation 0x23fa5035
5 WebCore 0x32ea308d
6 JavaScriptCore 0x2546dd51
7 JavaScriptCore 0x2546dcaf
8 libsystem_pthread.dylib 0x35e4c873
9 libsystem_pthread.dylib 0x35e4c7e7
10 libsystem_pthread.dylib 0x35e4a740
Thread 12 (AXSpeech):
0 libsystem_kernel.dylib 0x35d96164
1 CoreFoundation 0x24053905
2 CoreFoundation 0x24051c8d
3 CoreFoundation 0x23fa5249
4 CoreFoundation 0x23fa5035
5 Foundation 0x24d8f975
6 libAXSpeechManager.dylib 0x34694791
7 Foundation 0x24e60635
8 libsystem_pthread.dylib 0x35e4c873
9 libsystem_pthread.dylib 0x35e4c7e7
10 libsystem_pthread.dylib 0x35e4a740
Thread 13 :
0 libsystem_kernel.dylib 0x35daa0c4
1 libc++.1.dylib 0x34c468b9
2 JavaScriptCore 0x25819ee3
3 JavaScriptCore 0x25819cab
4 JavaScriptCore 0x2581b807
5 JavaScriptCore 0x2581b7a1
6 libsystem_pthread.dylib 0x35e4c873
7 libsystem_pthread.dylib 0x35e4c7e7
8 libsystem_pthread.dylib 0x35e4a740
Thread 14 (com.apple.coremedia.player.async):
0 libsystem_kernel.dylib 0x35d961b4
1 MediaToolbox 0x25c3479d
2 CoreMedia 0x2485ab41
3 libsystem_pthread.dylib 0x35e4c873
4 libsystem_pthread.dylib 0x35e4c7e7
5 libsystem_pthread.dylib 0x35e4a740
Thread 15 (WebCore: LocalStorage):
0 libsystem_kernel.dylib 0x35da9a60
1 libsystem_pthread.dylib 0x35e4ccb1
2 JavaScriptCore 0x25471577
3 WebKitLegacy 0x33ad8f7d
4 WebKitLegacy 0x33ad889d
5 JavaScriptCore 0x2546dd51
6 JavaScriptCore 0x2546dcaf
7 libsystem_pthread.dylib 0x35e4c873
8 libsystem_pthread.dylib 0x35e4c7e7
9 libsystem_pthread.dylib 0x35e4a740
Thread 16 :
0 libsystem_kernel.dylib 0x35d96164
1 CoreFoundation 0x24053905
2 CoreFoundation 0x24051c8d
3 CoreFoundation 0x23fa5249
4 CoreFoundation 0x23fa5035
5 TTSSpeechBundle 0x3512009
6 libsystem_pthread.dylib 0x35e4c873
7 libsystem_pthread.dylib 0x35e4c7e7
8 libsystem_pthread.dylib 0x35e4a740
Thread 17 (com.apple.coreaudio.AQClient):
0 libsystem_kernel.dylib 0x35d96164
1 CoreFoundation 0x24053905
2 CoreFoundation 0x24051c8d
3 CoreFoundation 0x23fa5249
4 CoreFoundation 0x23fa5035
5 AudioToolbox 0x2342c5ad
6 AudioToolbox 0x2341551f
7 libsystem_pthread.dylib 0x35e4c873
8 libsystem_pthread.dylib 0x35e4c7e7
9 libsystem_pthread.dylib 0x35e4a740
Thread 18 :
0 libsystem_kernel.dylib 0x35daa92c
1 libsystem_pthread.dylib 0x35e4a734 start_wqthread + 8
Thread 19 (com.apple.coremedia.player.async):
0 libsystem_kernel.dylib 0x35d961b4
1 MediaToolbox 0x25c3479d
2 CoreMedia 0x2485ab41
3 libsystem_pthread.dylib 0x35e4c873
4 libsystem_pthread.dylib 0x35e4c7e7
5 libsystem_pthread.dylib 0x35e4a740
Thread 21 :
0 libsystem_kernel.dylib 0x35daa92c
1 libsystem_pthread.dylib 0x35e4a734 start_wqthread + 8
Thread 22 :
0 libsystem_kernel.dylib 0x35daa92c
1 libsystem_pthread.dylib 0x35e4a734 start_wqthread + 8

Answer 1

At a minimum, this is UI code that is definitely running on a background queue:
if self.chartsSwitch.on {
I assume this line is as well:
chart["title"] = self.songTitleText.text
You cannot access UIKit on a background queue. You must collect all this data on the main queue, and pass it to things that run in the background.
I assume this entire block is actually on a background queue (since you load an NSData from an URL which should not be done on the main queue). In that case, this is a mutating UI change on a background queue:
indicator.startAnimation()
I wouldn't be surprised if there is more of this. You have to separate your model code and networking code from your UI code.