Crash: PFObject.saveInBackgroundWithBlock() causes crash.

[dtrenz]

When creating a new PFObject and using saveInBackgroundWithBlock(), the app crashes (only on device, not while attached to debugger).

Help is greatly appreciated.

Parse Version: 1.8.5 & 1.9.0

Here is the exception in the log:

[__NSPlaceholderArray initWithObjects:count:]: attempt to insert nil object from objects[1]

Here is the stack trace for the crashing thread:

Hardware Model:      iPhone7,2
Code Type:           ARM-64 (Native)
Parent Process:      launchd [1]
OS Version:          iOS 9.0.2 (13A452)

Exception Type:  EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note:  EXC_CORPSE_NOTIFY
Triggered by Thread:  0

Filtered syslog:
None found

Last Exception Backtrace:
0   CoreFoundation                  0x184434f5c __exceptionPreprocess + 124
1   libobjc.A.dylib                 0x19902bf80 objc_exception_throw + 56
2   CoreFoundation                  0x18431e30c -[__NSPlaceholderArray initWithObjects:count:] + 300
3   CoreFoundation                  0x184329db4 +[NSArray arrayWithObjects:count:] + 52
4   Parse                           0x100548220 -[PFTaskQueue enqueue:] (PFTaskQueue.m:44)
5   Parse                           0x1004d4fe8 -[PFObject saveInBackground] (PFObject.m:1989)
6   Parse                           0x1004d53b4 -[PFObject saveInBackgroundWithBlock:] (PFObject.m:2001)
7   Dojo                            0x100057110 0x100030000 + 160016
8   Dojo                            0x100043344 0x100030000 + 78660
9   Dojo                            0x100038744 0x100030000 + 34628
10  Dojo                            0x1000556ec 0x100030000 + 153324
11  Dojo                            0x1000557b0 0x100030000 + 153520
12  Dojo                            0x10005551c 0x100030000 + 152860
13  Dojo                            0x100055564 0x100030000 + 152932
14  Dojo                            0x10009da60 0x100030000 + 449120
15  libdispatch.dylib               0x1998257b0 _dispatch_call_block_and_release + 24
16  libdispatch.dylib               0x199825770 _dispatch_client_callout + 16
17  libdispatch.dylib               0x19982ae20 _dispatch_main_queue_callback_4CF + 1844
18  CoreFoundation                  0x1843ec258 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 12
19  CoreFoundation                  0x1843ea0c0 __CFRunLoopRun + 1628
20  CoreFoundation                  0x184318dc0 CFRunLoopRunSpecific + 384
21  GraphicsServices                0x18f46c088 GSEventRunModal + 180
22  UIKit                           0x1899f2f44 UIApplicationMain + 204
23  Dojo                            0x100042030 0x100030000 + 73776
24  libdyld.dylib                   0x1998568b8 start + 4

[parse-github-bot]

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[richardjrossiii]

It would appear from your stack trace that one of our internal tasks is nil, and from what I can tell, it seems loosely related to our PFCurrentUserController being nil.

If this crash is consistent, would you mind supplying us with some example code that reproduces the issue?

[dtrenz]

I believe that the code isn't very helpful, since it's just instantiating a PFObject via subclass, then calling saveInBackgroundWithBlock() on it.

Implementation:

let newMyObj= MyObj()

newMyObj.saveInBackgroundWithBlock { (success: Bool, error: NSError?) -> Void in
  if let error = error {
    log.error(error.localizedDescription)
  }

  if success {
    log.debug("MyObj created")
  }
}

MyObj.swift

import Parse

class MyObj : PFObject, PFSubclassing {

  @NSManaged var key: UInt

  override class func initialize() {
    struct Static {
      static var onceToken : dispatch_once_t = 0;
    }
    dispatch_once(&Static.onceToken) {
      self.registerSubclass()
    }
  }

  static func parseClassName() -> String {
    return "MyObj"
  }

}

[nlutsenko]

@dtrenz Any chance this is happening before you initialized Parse?
Before you call into saving - could you print to console your app id and/or client key from Parse.getApplicationId(). Just trying to make sure that it's initialized.

[dtrenz]

Ah ha! Thanks for pointing me in the right direction, @nlutsenko!

It appears that if I;

1. initialize Parse in application:didFinishLaunchingWithOptions,
2. then open another app (i.e. Safari) from my app,
3. then go back to my app...

...the initialized Parse SDK is no longer initialized.

Is this a bug, or should I move the Parse initialization to something like application:didBecomeActive in this scenario?

[nlutsenko]

Super strange. It should definitely be in application:didFinishLaunchingWithOptions:.
The only suggestions:

• move it to application:didFinishLaunchingWithOptions:
• move it to init() of your AppDelegate

Initializing the SDK multiple times is undefined. 😁

[dtrenz]

OK, that was a red herring.

I was using scheme env vars (NSProcessInfo.processInfo().environment) to set/read the Parse ID & key. But I didn't realize that they are only available when running the app attached to the debugger.

This was a painful lesson.

Thanks for helping to point me in the right direction.

[nlutsenko]

Glad you got it solved!

[dtrenz]

Me, too.

If there is a take-away for the Parse SDK, maybe there should be an error when a PFObject is saved before the Parse SDK has been initialized?