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  1. Realm Cocoa SDK
  2. RCOCOA-925

Unexpected iOS Crash: "Cannot register notification blocks from within write transactions."

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    • Type: Icon: Bug Bug
    • Resolution: Fixed
    • Priority: Icon: Unknown Unknown
    • None
    • Affects Version/s: None
    • Component/s: None

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      Goals

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      I want to help to fix the crash.

      Expected Results

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      No crash.

      Actual Results

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      Crash.

      Steps for others to Reproduce

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      Just run the demo project.

      Code Sample

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      realm-sample.zip

      Version of Realm and Tooling

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      ProductName:	Mac OS X
ProductVersion:	10.15.6
BuildVersion:	19G2021

/Applications/Xcode.app/Contents/Developer
Xcode 12.0
Build version 12A7209

/usr/local/bin/pod
1.9.3
Realm (5.5.0)
RealmSwift (5.5.0)
Realm (from `https//github.com/realm/realm-cocoa.git`, tag `v5.5.0`)
RealmSwift (from `https//github.com/realm/realm-cocoa.git`, tag `v5.5.0`)

/bin/bash
GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin19)

carthage not found
(not in use here)

/usr/bin/git
git version 2.24.3 (Apple Git-128)

      Description

      It looks like that if a Realm.write { }}} is executed on the same thread as the {{Results.observe { }}}, the write transaction is not fully closed before the observe callback gets invoked. In the provided code example, the observe callback contains a {{ViewController2.beginAppearanceTransition() call which leads to the ViewController2.viewWillAppear() being called during the write transaction. The Problem is that the ViewController2.viewWillAppear() contains a {{Results.observe { }}} as well which leads to the error described in the stack trace below.

      Stack trace

      2020-10-14 15:17:12.918034+0200 realm-sample[46718:1573132] *** Terminating app due to uncaught exception 'RLMException', reason: 'Cannot register notification blocks from within write transactions.'
*** First throw call stack:
(
	0   CoreFoundation                      0x0000000108414126 __exceptionPreprocess + 242
	1   libobjc.A.dylib                     0x00000001057b3f78 objc_exception_throw + 48
	2   Realm                               0x00000001067981db -[RLMRealm verifyNotificationsAreSupported:] + 363
	3   Realm                               0x00000001066736f2 _Z23RLMAddNotificationBlockI10RLMResultsEP20RLMNotificationTokenPT_U13block_pointerFvP11objc_objectP19RLMCollectionChangeP7NSErrorEPU28objcproto17OS_dispatch_queue8NSObject + 370
	4   Realm                               0x00000001067c6b4e -[RLMResults addNotificationBlock:queue:] + 78
	5   RealmSwift                          0x0000000104e63099 $s10RealmSwift7ResultsV7observe2on_So20RLMNotificationTokenCSo17OS_dispatch_queueCSg_yAA0A16CollectionChangeOyACyxGGctF + 489
	6   realm-sample                        0x0000000104ab2e32 $s12realm_sample15ViewController2C14viewWillAppearyySbF + 354
	7   realm-sample                        0x0000000104ab3048 $s12realm_sample15ViewController2C14viewWillAppearyySbFTo + 56
	8   UIKitCore                           0x00000001116aefb2 -[UIViewController _setViewAppearState:isAnimating:] + 654
	9   UIKitCore                           0x00000001116af7db -[UIViewController __viewWillAppear:] + 106
	10  realm-sample                        0x0000000104ab2005 $s12realm_sample14ViewControllerC13viewDidAppearyySbFy10RealmSwift0H16CollectionChangeOyAE7ResultsVyAA0H6ObjectCGGcfU_ + 85
	11  RealmSwift                          0x0000000104e63114 $s10RealmSwift0A16CollectionChangeOyAA7ResultsVyxGGIegg_AGIegn_AA0aC5ValueRzlTR + 52
	12  RealmSwift                          0x0000000104e53b09 $s10RealmSwift20ObservableCollectionPAAE16wrapObserveBlockyy011BackingObjcD0QzSg_So19RLMCollectionChangeCSgs5Error_pSgtcyAA0adK0OyxGcFyAG_AjLtcfU_ + 1625
	13  RealmSwift                          0x0000000104e541aa $s10RealmSwift20ObservableCollectionPAAE16wrapObserveBlockyy011BackingObjcD0QzSg_So19RLMCollectionChangeCSgs5Error_pSgtcyAA0adK0OyxGcFyAG_AjLtcfU_TA + 106
	14  RealmSwift                          0x0000000104e235b4 $sSo10RLMResultsCyyXlGSgSo19RLMCollectionChangeCSgs5Error_pSgIegngg_AdgIIegggg_TR + 84
	15  RealmSwift                          0x0000000104e236c1 $sSo10RLMResultsCyyXlGSgSo19RLMCollectionChangeCSgs5Error_pSgIegggg_AdGSo7NSErrorCSgIeyByyy_TR + 161
	16  Realm                               0x000000010667b684 _ZN12_GLOBAL__N_125CollectionCallbackWrapperclERKN5realm19CollectionChangeSetESt13exception_ptr + 388
	17  Realm                               0x000000010667b315 _ZN5realm24CollectionChangeCallback4ImplIN12_GLOBAL__N_125CollectionCallbackWrapperEE5afterERKNS_19CollectionChangeSetE + 69
	18  Realm                               0x0000000106531436 _ZN5realm24CollectionChangeCallback5afterERKNS_19CollectionChangeSetE + 38
	19  Realm                               0x0000000106531399 _ZZN5realm5_impl18CollectionNotifier13after_advanceEvENK4$_10clINS_4util17CheckedUniqueLockENS1_8CallbackEEEDaRT_RT0_ + 169
	20  Realm                               0x0000000106510ae4 _ZN5realm5_impl18CollectionNotifier17for_each_callbackIZNS1_13after_advanceEvE4$_10EEvOT_ + 148
	21  Realm                               0x0000000106510a49 _ZN5realm5_impl18CollectionNotifier13after_advanceEv + 25
	22  Realm                               0x0000000106511ce0 _ZN5realm5_impl15NotifierPackage13after_advanceEv + 336
	23  Realm                               0x00000001068e3548 _ZN12_GLOBAL__N_126advance_with_notificationsIZN5realm5_impl11transaction5beginERKNSt3__110shared_ptrINS1_11TransactionEEEPNS1_14BindingContextERNS2_15NotifierPackageEE3$_2EEvSB_S9_OT_SD_ + 1208
	24  Realm                               0x00000001068e3081 _ZN5realm5_impl11transaction5beginERKNSt3__110shared_ptrINS_11TransactionEEEPNS_14BindingContextERNS0_15NotifierPackageE + 49
	25  Realm                               0x00000001065e146c _ZN5realm5_impl16RealmCoordinator16promote_to_writeERNS_5RealmE + 316
	26  Realm                               0x0000000106852271 _ZN5realm5Realm17begin_transactionEv + 545
	27  Realm                               0x0000000106798cac -[RLMRealm beginWriteTransactionWithError:] + 44
	28  Realm                               0x0000000106798c78 -[RLMRealm beginWriteTransaction] + 40
	29  RealmSwift                          0x0000000104e458b5 $s10RealmSwift0A0V10beginWriteyyF + 53
	30  RealmSwift                          0x0000000104e4552f $s10RealmSwift0A0V5write16withoutNotifying_xSaySo20RLMNotificationTokenCG_xyKXEtKlF + 223
	31  realm-sample                        0x0000000104ab1e55 $s12realm_sample14ViewControllerC13viewDidAppearyySbF + 645
	32  realm-sample                        0x0000000104ab2218 $s12realm_sample14ViewControllerC13viewDidAppearyySbFTo + 56
	33  UIKitCore                           0x00000001116af0bc -[UIViewController _setViewAppearState:isAnimating:] + 920
	34  UIKitCore                           0x00000001116afa93 -[UIViewController __viewDidAppear:] + 146
	35  UIKitCore                           0x00000001116afd6c -[UIViewController _endAppearanceTransition:] + 232
	36  UIKitCore                           0x0000000111583b66 __48-[UIPresentationController transitionDidFinish:]_block_invoke + 138
	37  UIKitCore                           0x00000001122ce97a -[_UIAfterCACommitBlock run] + 54
	38  UIKitCore                           0x0000000111de785d _runAfterCACommitDeferredBlocks + 333
	39  UIKitCore                           0x0000000111dd7790 _cleanUpAfterCAFlushAndRunDeferredBlocks + 221
	40  UIKitCore                           0x0000000111e09154 _afterCACommitHandler + 85
	41  CoreFoundation                      0x00000001083816b3 __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__ + 23
	42  CoreFoundation                      0x000000010837bf3f __CFRunLoopDoObservers + 547
	43  CoreFoundation                      0x000000010837c4e2 __CFRunLoopRun + 1113
	44  CoreFoundation                      0x000000010837bb9e CFRunLoopRunSpecific + 567
	45  GraphicsServices                    0x00000001102f7db3 GSEventRunModal + 139
	46  UIKitCore                           0x0000000111dd8af3 -[UIApplication _run] + 912
	47  UIKitCore                           0x0000000111ddda04 UIApplicationMain + 101
	48  libswiftUIKit.dylib                 0x0000000107c9b7b2 $s5UIKit17UIApplicationMainys5Int32VAD_SpySpys4Int8VGGSgSSSgAJtF + 98
	49  realm-sample                        0x0000000104ab43aa $sSo21UIApplicationDelegateP5UIKitE4mainyyFZ + 122
	50  realm-sample                        0x0000000104ab431e $s12realm_sample11AppDelegateC5$mainyyFZ + 46
	51  realm-sample                        0x0000000104ab43f9 main + 41
	52  libdyld.dylib                       0x0000000107ebd415 start + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
terminating with uncaught exception of type NSException
CoreSimulator 732.17 - Device: iPhone 6s (875C55C5-F7E8-4881-AC23-C82BD2503BE2) - Runtime: iOS 14.0 (18A372) - DeviceType: iPhone 6s
*** Terminating app due to uncaught exception 'RLMException', reason: 'Cannot register notification blocks from within write transactions.'

            Assignee:
            Unassigned Unassigned
            Reporter:
            unitosyncbot Unito Sync Bot
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              Created:
              Updated:
              Resolved: