🐛 [Banner Ad] 'Fatal Exception: NSInvalidArgumentException' in iOS

Bug report

Describe the bug The iOS (Swift) app crashes randomly, but often, when banners are loaded with the error:

Fatal Exception: NSInvalidArgumentException
*** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[0]

Stack Trace

Fatal Exception: NSInvalidArgumentException
0  CoreFoundation                 0x1a4b33180 __exceptionPreprocess
1  libobjc.A.dylib                0x1a3d0b9f8 objc_exception_throw
2  CoreFoundation                 0x1a4aacbec _CFArgv
3  CoreFoundation                 0x1a4a34898 -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]
4  CoreFoundation                 0x1a4a25474 +[NSDictionary dictionaryWithObjects:forKeys:count:]
5  Runner                         0x1012cff2c -[FLTAdInstanceManager onAdLoaded:] + 82 (FLTAdInstanceManager_Internal.m:82)
6  Runner                         0x1012ce174 -[FLTBannerAd adViewDidReceiveAd:] + 150 (FLTAd_Internal.m:150)
7  Runner                         0x1011d4824 GAD_GADBannerView_arm64_7_69_0
8  Runner                         0x10122a058 __copy_helper_block_e8_32s40s48s56s64b72w
9  Runner                         0x10122a114 __copy_helper_block_e8_32s40s48s56s64b72w
10 Runner                         0x101229d08 GAD_GADInternalBannerView_arm64_7_69_0
11 Runner                         0x1012298d0 GAD_GADInternalBannerView_arm64_7_69_0
12 Runner                         0x101229f80 GAD_GADInternalBannerView_arm64_7_69_0
13 libdispatch.dylib              0x1a4570a38 _dispatch_call_block_and_release
14 libdispatch.dylib              0x1a45717d4 _dispatch_client_callout
15 libdispatch.dylib              0x1a451f008 _dispatch_main_queue_callback_4CF$VARIANT$mp
16 CoreFoundation                 0x1a4ac4b20 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__
17 CoreFoundation                 0x1a4abfa58 __CFRunLoopRun
18 CoreFoundation                 0x1a4abefb4 CFRunLoopRunSpecific
19 GraphicsServices               0x1a6cc079c GSEventRunModal
20 UIKitCore                      0x1d1320c38 UIApplicationMain
21 Runner                         0x100fb37d8 main + 6 (AppDelegate.swift:6)
22 libdyld.dylib                  0x1a45828e0 start

Steps to reproduce

Steps to reproduce the behavior:

1. Create a Flutter project (Swift).
2. Insert an inline banner as described in the codelabs (in a ListView).
3. The error will appear randomly.

Expected behavior

The app should not crash.

---

Additional context

I have not been able to reproduce the error continuously but many of my users have encountered it as I can see from the crashlytics logs.

I have mediation with MoPub, Facebook Audience Network and AdColony configured but the error also occurs if I pause it.

---

Flutter doctor

Run flutter doctor and paste the output below:

Click To Expand

[✓] Flutter (Channel stable, 2.0.3, on Mac OS X 10.15.7 19H2 darwin-x64, locale it-IT)
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
[✓] Xcode - develop for iOS and macOS
[✓] Chrome - develop for the web
[✓] Android Studio (version 4.1)
[✓] VS Code (version 1.54.3)
[✓] Connected device (3 available)

• No issues found!

---

Flutter dependencies

Run flutter pub deps -- --style=compact and paste the output below:

Click To Expand

Dart SDK 2.12.2
Flutter SDK 2.0.3

dependencies:
- admob_consent 1.1.2 [flutter]
- apple_sign_in 0.1.0 [flutter]
- async 2.5.0 [collection]
- auto_size_text 2.1.0 [flutter]
- cached_network_image 3.0.0-nullsafety [flutter flutter_cache_manager octo_image]
- camera 0.8.0 [flutter camera_platform_interface pedantic quiver]
- carousel_slider 3.0.0 [flutter]
- circular_check_box 1.0.4 [flutter]
- cloud_firestore 1.0.2 [cloud_firestore_platform_interface cloud_firestore_web firebase_core firebase_core_platform_interface flutter meta]
- connectivity_widget 0.1.7 [flutter rxdart connectivity stream_disposable http]
- cupertino_icons 1.0.2
- dio 4.0.0-prev3 [http_parser path]
- easy_debounce 1.0.2 [flutter]
- equatable 2.0.0 [collection meta]
- expandable 5.0.1 [flutter]
- extended_image 3.0.0 [extended_image_library flutter meta]
- firebase_analytics 7.1.1 [firebase_analytics_platform_interface firebase_analytics_web firebase_core flutter meta]
- firebase_auth 1.0.1 [firebase_auth_platform_interface firebase_auth_web firebase_core firebase_core_platform_interface flutter meta]
- firebase_core 1.0.2 [firebase_core_platform_interface firebase_core_web flutter meta]
- firebase_crashlytics 1.0.0 [firebase_core firebase_core_platform_interface firebase_crashlytics_platform_interface flutter stack_trace]
- firebase_messaging 9.0.1 [firebase_core firebase_core_platform_interface firebase_messaging_platform_interface firebase_messaging_web flutter meta]
- firebase_storage 8.0.0 [firebase_core firebase_core_platform_interface firebase_storage_platform_interface firebase_storage_web flutter]
- flag 5.0.0-nullsafety [flutter flutter_svg]
- flutter 0.0.0 [characters collection meta typed_data vector_math sky_engine]
- flutter_facebook_auth 3.1.1 [flutter flutter_facebook_auth_platform_interface flutter_facebook_auth_web]
- flutter_image_compress 0.7.0 [flutter]
- flutter_localizations 0.0.0 [flutter intl characters clock collection meta path typed_data vector_math]
- flutter_rating_bar 4.0.0 [flutter]
- flutter_signin_button 2.0.0-nullsafety.0 [flutter font_awesome_flutter]
- font_awesome_flutter 9.0.0 [flutter]
- get 3.26.0 [flutter]
- google_fonts 2.0.0 [flutter http path_provider crypto]
- google_mobile_ads 0.11.0+4 [meta flutter]
- google_sign_in 5.0.1 [google_sign_in_platform_interface google_sign_in_web flutter meta]
- http 0.13.1 [http_parser meta path pedantic]
- image 3.0.2 [archive meta xml]
- image_editor 1.0.0 [flutter]
- image_gallery_saver 1.6.8 [flutter]
- image_picker 0.7.3 [flutter flutter_plugin_android_lifecycle image_picker_platform_interface image_picker_for_web]
- in_app_review 2.0.1 [flutter in_app_review_platform_interface]
- intl 0.17.0 [clock path]
- intl_utils 2.1.0 [analyzer archive args http intl path petitparser yaml]
- introduction_screen 2.0.0 [flutter dots_indicator]
- isolate 2.0.3
- lottie 1.0.1 [archive characters charcode collection flutter logging meta path vector_math]
- matrix4_transform 2.0.0 [flutter]
- modal_bottom_sheet 2.0.0 [flutter]
- native_shared_preferences 1.0.5 [flutter meta]
- ndialog 4.0.1 [flutter]
- ntp 1.0.8 [universal_io]
- package_info 2.0.0 [flutter]
- page_view_indicators 2.0.0 [flutter]
- path_drawing 0.5.0-nullsafety.0 [vector_math meta path_parsing flutter]
- path_provider 2.0.1 [flutter path_provider_platform_interface path_provider_macos path_provider_linux path_provider_windows]
- permission_handler 6.1.1 [flutter meta permission_handler_platform_interface]
- photo_view 0.11.1 [flutter]
- provider 5.0.0 [collection flutter nested]
- purchases_flutter 3.1.0 [flutter collection]
- rxdart 0.26.0
- screenshot 0.3.0 [flutter]
- share_plus 2.0.0 [meta mime flutter share_plus_platform_interface share_plus_linux share_plus_macos share_plus_windows share_plus_web]
- shared_preferences 2.0.5 [meta flutter shared_preferences_platform_interface shared_preferences_linux shared_preferences_macos shared_preferences_web shared_preferences_windows]
- svg_path_parser 1.0.0 [string_scanner flutter]
- syncfusion_flutter_charts 18.4.49 [flutter intl vector_math syncfusion_flutter_core]
- timeago 3.0.2
- trotter 1.2.0
- url_launcher 6.0.2 [flutter url_launcher_platform_interface url_launcher_linux url_launcher_macos url_launcher_windows url_launcher_web]
- video_player 2.0.2 [meta video_player_platform_interface video_player_web flutter flutter_test]

transitive dependencies:
- _fe_analyzer_shared 19.0.0 [meta]
- analyzer 1.3.0 [_fe_analyzer_shared cli_util collection convert crypto glob meta package_config path pub_semver source_span watcher yaml pedantic]
- archive 3.1.2 [crypto path]
- args 2.0.0
- boolean_selector 2.1.0 [source_span string_scanner]
- camera_platform_interface 2.0.1 [flutter meta plugin_platform_interface cross_file stream_transform]
- characters 1.1.0
- charcode 1.2.0
- cli_util 0.3.0 [meta path]
- clock 1.1.0
- cloud_firestore_platform_interface 4.0.0 [collection firebase_core flutter meta plugin_platform_interface]
- cloud_firestore_web 1.0.2 [cloud_firestore_platform_interface firebase_core firebase_core_web flutter flutter_web_plugins js]
- collection 1.15.0
- connectivity 3.0.3 [flutter meta connectivity_platform_interface connectivity_macos connectivity_for_web]
- connectivity_for_web 0.4.0 [connectivity_platform_interface flutter_web_plugins flutter]
- connectivity_macos 0.2.0 [flutter]
- connectivity_platform_interface 2.0.1 [flutter meta plugin_platform_interface]
- convert 3.0.0 [typed_data]
- cross_file 0.3.1+1 [flutter meta]
- crypto 3.0.0 [collection typed_data]
- dots_indicator 2.0.0 [flutter]
- extended_image_library 2.0.2 [crypto flutter http_client_helper path path_provider]
- fake_async 1.2.0 [clock collection]
- ffi 1.0.0
- file 6.1.0 [meta path]
- firebase 9.0.1 [http http_parser js]
- firebase_analytics_platform_interface 1.1.0 [flutter meta]
- firebase_analytics_web 0.2.0+1 [firebase firebase_analytics_platform_interface flutter flutter_web_plugins meta]
- firebase_auth_platform_interface 4.0.0 [firebase_core flutter meta plugin_platform_interface]
- firebase_auth_web 1.0.3 [firebase_auth_platform_interface firebase_core firebase_core_web flutter flutter_web_plugins http_parser intl js meta]
- firebase_core_platform_interface 4.0.0 [flutter meta plugin_platform_interface]
- firebase_core_web 1.0.2 [firebase_core_platform_interface flutter flutter_web_plugins js meta]
- firebase_crashlytics_platform_interface 2.0.0 [collection firebase_core flutter meta plugin_platform_interface]
- firebase_messaging_platform_interface 2.0.1 [firebase_core flutter meta plugin_platform_interface]
- firebase_messaging_web 1.0.2 [firebase_core firebase_core_web firebase_messaging_platform_interface flutter flutter_web_plugins js meta]
- firebase_storage_platform_interface 2.0.0 [collection firebase_core flutter meta plugin_platform_interface]
- firebase_storage_web 1.0.2 [async firebase_core firebase_core_web firebase_storage_platform_interface flutter flutter_web_plugins http js meta]
- flutter_blurhash 0.5.4-nullsafety.0 [flutter meta pedantic]
- flutter_cache_manager 3.0.0-nullsafety.2 [clock collection file flutter http image path path_provider pedantic rxdart sqflite uuid]
- flutter_facebook_auth_platform_interface 2.1.1 [flutter plugin_platform_interface]
- flutter_facebook_auth_web 2.1.1 [flutter flutter_web_plugins js flutter_facebook_auth_platform_interface]
- flutter_plugin_android_lifecycle 2.0.0 [flutter]
- flutter_svg 0.21.0-nullsafety.0 [flutter meta path_drawing vector_math xml]
- flutter_test 0.0.0 [flutter test_api path fake_async clock stack_trace vector_math async boolean_selector characters charcode collection matcher meta source_span stream_channel string_scanner term_glyph typed_data]
- flutter_web_plugins 0.0.0 [flutter js characters collection meta typed_data vector_math]
- glob 2.0.0 [async collection file path pedantic string_scanner]
- google_sign_in_platform_interface 2.0.1 [flutter meta quiver]
- google_sign_in_web 0.10.0 [google_sign_in_platform_interface flutter flutter_web_plugins meta js]
- http_client_helper 2.0.2 [http]
- http_parser 4.0.0 [charcode collection source_span string_scanner typed_data]
- image_picker_for_web 2.0.0 [image_picker_platform_interface meta flutter flutter_web_plugins]
- image_picker_platform_interface 2.0.1 [flutter meta http plugin_platform_interface]
- in_app_review_platform_interface 2.0.2 [flutter url_launcher plugin_platform_interface platform]
- js 0.6.3
- logging 1.0.0
- matcher 0.12.10 [stack_trace]
- meta 1.3.0
- mime 1.0.0
- nested 1.0.0 [flutter]
- octo_image 1.0.0-nullsafety.1 [flutter flutter_blurhash]
- package_config 2.0.0 [path]
- path 1.8.0
- path_parsing 0.2.0-nullsafety.0 [vector_math meta]
- path_provider_linux 2.0.0 [path xdg_directories path_provider_platform_interface flutter]
- path_provider_macos 2.0.0 [flutter]
- path_provider_platform_interface 2.0.1 [flutter meta platform plugin_platform_interface]
- path_provider_windows 2.0.0 [path_provider_platform_interface meta path flutter ffi win32]
- pedantic 1.11.0
- permission_handler_platform_interface 3.1.1 [flutter meta plugin_platform_interface]
- petitparser 4.0.2 [meta]
- platform 3.0.0
- plugin_platform_interface 2.0.0 [meta]
- process 4.2.0 [file path platform]
- pub_semver 2.0.0 [collection]
- quiver 3.0.0 [matcher]
- share_plus_linux 2.0.0 [share_plus_platform_interface file flutter meta url_launcher]
- share_plus_macos 2.0.0 [share_plus_platform_interface flutter]
- share_plus_platform_interface 2.0.0 [flutter meta mime plugin_platform_interface]
- share_plus_web 2.0.0 [share_plus_platform_interface url_launcher flutter flutter_web_plugins meta]
- share_plus_windows 2.0.0 [share_plus_platform_interface flutter meta url_launcher]
- shared_preferences_linux 2.0.0 [flutter file meta path path_provider_linux shared_preferences_platform_interface]
- shared_preferences_macos 2.0.0 [shared_preferences_platform_interface flutter]
- shared_preferences_platform_interface 2.0.0 [flutter]
- shared_preferences_web 2.0.0 [shared_preferences_platform_interface flutter flutter_web_plugins meta]
- shared_preferences_windows 2.0.0 [shared_preferences_platform_interface flutter file meta path path_provider_platform_interface path_provider_windows]
- sky_engine 0.0.99
- source_span 1.8.0 [charcode collection path term_glyph]
- sqflite 2.0.0+3 [flutter sqflite_common path]
- sqflite_common 2.0.0+2 [synchronized path meta]
- stack_trace 1.10.0 [path]
- stream_channel 2.1.0 [async]
- stream_disposable 0.1.0 [flutter]
- stream_transform 2.0.0
- string_scanner 1.1.0 [charcode source_span]
- syncfusion_flutter_core 18.4.49 [flutter]
- synchronized 3.0.0
- term_glyph 1.2.0
- test_api 0.2.19 [async boolean_selector collection meta path source_span stack_trace stream_channel string_scanner term_glyph matcher]
- typed_data 1.3.0 [collection]
- universal_io 1.0.1 [meta zone_local]
- url_launcher_linux 2.0.0 [flutter]
- url_launcher_macos 2.0.0 [flutter]
- url_launcher_platform_interface 2.0.2 [flutter plugin_platform_interface]
- url_launcher_web 2.0.0 [url_launcher_platform_interface meta flutter flutter_web_plugins]
- url_launcher_windows 2.0.0 [flutter]
- uuid 3.0.2 [crypto]
- vector_math 2.1.0
- video_player_platform_interface 4.0.0 [flutter meta flutter_test]
- video_player_web 2.0.0 [flutter flutter_web_plugins meta video_player_platform_interface]
- watcher 1.0.0 [async path pedantic]
- win32 2.0.4 [ffi]
- xdg_directories 0.2.0 [meta path process]
- xml 5.0.2 [collection meta petitparser]
- yaml 3.1.0 [collection source_span string_scanner]
- zone_local 0.1.2

---

[numen31337]

Crashes here as adIdFor might return nil:

- (void)onAdFailedToLoad:(id<FLTAd> _Nonnull)ad error:(FLTLoadAdError *_Nonnull)error {
  [_channel invokeMethod:@"onAdEvent"
               arguments:@{
                 @"adId" : [self adIdFor:ad],  //<=== Crash
                 @"eventName" : @"onAdFailedToLoad",
                 @"loadAdError" : error
               }];
}

adIdFor implementation:

- (NSNumber *_Nullable)adIdFor:(id<FLTAd> _Nonnull)ad {
  NSArray<NSNumber *> *keys = [_ads allKeysForObject:ad];

  if (keys.count > 1) {
    NSLog(@"%@Error: Multiple keys for a single ad.",
          NSStringFromClass([FLTAdInstanceManager class]));
  }

  if (keys.count > 0) {
    return keys[0];
  }

  return nil; //<=== This will crash dictionary creation
}

[ThrowJojo]

Someone has been assigned to this issue now so I think it will be fixed sometime soon 👍