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EventDispatcher in GameMode broken on 4.6?

  • make an event dispatcher on custom game mode

  • call it once on begin play

  • use it in custom hud / custom player

  • use the Standalone mode or make a build

it works fine with 4.5.1 and is completely broken in 4.6. Player and hud get ignored at the start. Level loads fine but no hud and no working default pawn class.

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Please note that upon opening the project for the first time with 4.6 I observed the following error... But hitting compile solved the problem(?!)

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Btw, the compile error will reoccur every time the project is reopened. Then I hit compile and it goes away. But Standalone mode or builds won't work properly.

Product Version: Not Selected
b1.png (143.6 kB)
b2.png (100.4 kB)
b3.png (89.2 kB)
b4.png (64.8 kB)
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asked Dec 04 '14 at 07:53 AM in Bug Reports

avatar image

1.8k 66 27 90

avatar image keyle Dec 04 '14 at 08:26 AM

Is it a compile order issue? Where game mode would be compiled after hud and player causing an issue from a clean build?

avatar image keyle Dec 04 '14 at 08:32 AM
  • refresh all nodes

  • compile OK

  • launch Standalone game

    MachineId:23F563844A04271878FE6C85FB93C956 EpicAccountId:

    Access violation - code c0000005 (first/second chance not available)

    UE4Editor_UnrealEd + 3154877 bytes UE4Editor_UnrealEd + 3206223 bytes UE4Editor_UnrealEd + 9878186 bytes UE4Editor_UnrealEd + 9617164 bytes UE4Editor_CoreUObject + 626800 bytes UE4Editor_CoreUObject + 946322 bytes [...] UE4Editor_Engine + 9512678 bytes UE4Editor_Engine + 9260885 bytes UE4Editor_Engine + 3802230 bytes UE4Editor_Engine + 3703790 bytes UE4Editor!FEngineLoop::Init() + 1147 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.6\engine\source\runtime\launch\private\launchengineloop.cpp:1919] UE4Editor!GuardedMain() + 292 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.6\engine\source\runtime\launch\private\launch.cpp:126] UE4Editor!GuardedMainWrapper() + 26 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.6\engine\source\runtime\launch\private\windows\launchwindows.cpp:126] UE4Editor!WinMain() + 249 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.6\engine\source\runtime\launch\private\windows\launchwindows.cpp:202] UE4Editor!__tmainCRTStartup() + 329 bytes [f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c:618]

avatar image Dredok Dec 04 '14 at 08:35 AM

I have experienced this kind of behavior a lot ... using eventDispatchers in UMG widgets with parameters (weird) or using them on GameModes and GameInstance (singletons). It does not work properly either on PlayerController ... I used a workaround that most of the time works for me which consists on using a Blueprint to handle all eventDispatchers. It might work for you...

avatar image keyle Dec 04 '14 at 08:46 AM

Thanks @Dredok

avatar image paradoc Dec 08 '14 at 04:25 PM

can you explain this concept a little? previously my dispatchers were coming from game mode or controller to help communicate with the persistent level. but since that is currently not working, i'm interested to know how a separate blueprint could handle this. does the new blueprint have an actor base class? do you spawn an instance of it on beginplays of your game mode or controller?

[EDIT] just to expound upon this a bit, that workaround is really helpful. basically, in my player controller i spawned an event dispatcher manager class and stored it in a variable. then, from all other classes i can access that player controller's variable to execute whichever event dispatcher. no crashes or corrupt blueprints as a result of this method thus far.

avatar image keyle Dec 04 '14 at 01:04 PM

@staff I believe this is what the problem is

 [2014.12.04-13.02.22:898][  0]LogBlueprint:Error: [compiler] Error No delegate function ''  WeaponChangeDispatcher_Event_0 
 [2014.12.04-13.02.22:899][  0]LogBlueprint:Error: [compiler] Error Wrong Event Dispatcher. Refresh node  Assign Weapon Change Dispatcher 
 [2014.12.04-13.02.22:899][  0]LogBlueprint:Error: [compiler] Error Failed to create property K2Node_CreateDelegate_OutputDelegate from  OutputDelegate  due to a bad or unknown type (Delegate)
 [2014.12.04-13.02.22:900][  0]LogBlueprint:Error: [compiler] Error Event signature error:  Signature not found.  WeaponChangeDispatcher_Event_0 
 [2014.12.04-13.02.22:905][  0]LogBlueprint:Warning: [compiler] Warning [0018.50] Compile of GameHud failed. 4 Fatal Issue(s) 0 Warning(s) [in 16 ms]

avatar image keyle Dec 04 '14 at 01:23 PM

I have found a work around. Instead of having the dispatcher in the GameMode BP, I put it in the PlayerController. Hud hooks onto that, so does player character, and the dispatching is done by the GameMode (For now). All seems to work and no Failure are appearing in logs anymore.

It may look like it's a compile order issue from a clean.

avatar image Doug E ♦♦ STAFF Dec 04 '14 at 05:45 PM

Hey keyle-

I'm attempting to reproduce the event dispatcher bug you described but I need a little clarification on your setup. Are the screenshots you provided from your GameMode BP or the HUD/Player BP?


avatar image CombatJack Dec 04 '14 at 07:43 PM
avatar image CombatJack Dec 04 '14 at 11:41 PM

Repro steps in my cross linked issue.

avatar image keyle Dec 04 '14 at 11:44 PM


  • b1.png - player character BP (set projectile)

  • b2.png - game hud BP (set hud graphic)

  • b3.png - game mode BP (hook up 1,2,3 keys to dispatch)

  • b4.png - shows the HUD after a project closed/opened


avatar image paradoc Dec 06 '14 at 07:09 PM

I've had this issue in 4.6 as well. my bug Event Dispatcher Bug can probably be closed out in favor of this one.

In my case, migrated files with bindings would no longer appear during runtime as well.

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2 answers: sort voted first

Hey keyle-

I have written bug report UE-6396 and submitted it to our bug database so that our engineers can investigate this issue further.


Doug Wilson

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answered Dec 08 '14 at 05:26 PM

avatar image keyle Dec 12 '14 at 07:53 AM

Should it be marked as Resolved if all that's been done is a ticket being raised?

avatar image Doug E ♦♦ STAFF Dec 12 '14 at 05:33 PM

Hey keyle-

Are you unable to use event dispatchers in other blueprints as well or does this only occur when using the custom GameMode BP?

avatar image keyle Dec 13 '14 at 01:29 AM

Hey Doug,

I guess my point is that this is marked as resolved while it's not resolved for users. The creation of a ticket - which I can't track - does not solve the problem for Users.

To reiterate, my work around is currently to not use the GameMode BP but use the player controller instead. I wouldn't consider your answer as Resolved, as there is no linked ticket, or fix version for this issue for Users.

This only occurs to custom GameMode BP indeed. For me anyway.

Where can I track UE-tickets, even Read-only?

avatar image bleeds187 Dec 12 '14 at 09:47 PM


We were having the same issue as described above and, specifically with EventDispatchers in a BP of PlayerController that are subscribed to from within a UMG widget (using GetOwningPlayer->CastToOurBPPC). The error messages will show up until you compile the Widget that is subscribing; additionally these callbacks are broken in cooked builds regardless of compiling the Widget. We have other dispatchers that do not appear to be broken, however, any custom events in our Widgets that subscribe to dispatchers appear to be whats affected.

Fortunately I was able to check the differences between 4.5 and 4.6 (using Perforce actually, I am at a studio that is a licensee and am posting in AnswerHub as opposed to UDN because this post already existed with Epic eyes on it). It looks like what broke this is CL#2308582, specifically the changes to //depot/UE4/Engine/Source/Editor/BlueprintGraph/Private/K2Node_MCDelegate.cpp [revision 33]

I reverted the changed code from this CL (only the changes in K2Node_MCDelegate.cpp) to the code that was in 4.5 and everything is now working for us. We are still testing this locally but so far it seems to be the remedy for our dispatcher regression in 4.6.

Hope that helps.

p.s. Anyone that wants to try what I am describing in their 4.6 code simply replace the implementation of UK2Node_BaseMCDelegate::AllocateDefaultPins() and UK2Node_BaseMCDelegate::GetDelegateSignature() in their 4.6 code using the functions from 4.5 found below:


avatar image Slonopotamus Dec 12 '14 at 09:52 PM

Great that you found problematic commit. Note that this isn't the only thing it broke.

avatar image Doug E ♦♦ STAFF Dec 12 '14 at 09:55 PM

Thanks bleeds187 for the additional information. This has been added to the report currently being investigated.

avatar image SpEXyPHe Dec 15 '14 at 01:58 PM

I would like to add that our project is reliang HEAVILY on the process of dispatching.

Because of this bug our entire project is at risk....!

As extra information: We have noticed that recompiling every blueprint (in the engine environment) with a dispatcher link, then use 'save all' and then running the game in a new editor window does temporarily remove our issues. However reopening or using the 'standalone game' does bring it back.

We dearly hope that a solution is found as soon as possible.

avatar image keyle Dec 16 '14 at 12:08 AM

@SpEXyPHe Exact same issue here. In my experience, if you have a compile error when the project just opened, it will not work properly in a standalone game. For now, use PlayerController for event dispatchers and/or avoid GameMode event dispatchers. As Doug indicated, it's been fixed and hopefully 4.6.1 is not too far away.

avatar image buscas31 Jan 12 '15 at 04:43 PM

When you guys from epic go to provide a update to 4.6 version to solve this bug with event dispatcher? Because with this bug active, i can not do anything right in my project. I use this event a lot. I´m thinking to go back to 4.5 to avoid this kind of bug.... :(

avatar image paradoc Jan 12 '15 at 05:01 PM

if you're at a standstill, the workaround posted above works really well. create a separate class (i called mine eventDispatcherManager), and in that class create the desired event dispatcher. then in your game mode, spawn an instance of that class, and store it in a variable. then you can access any event you want, and it also provides a single point of control for all events.

avatar image Doug E ♦♦ STAFF Jan 12 '15 at 07:11 PM

Hey buscas31 and paradoc-

There have been a number of fixes to event dispatchers in the engine. Could you test using event dispatchers from the game mode in the latest 4.7 preview (preview 2) and see if it's working for you there.


Doug Wilson

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Hey everyone-

This issue has been resolved in our main internal branch and will be included in a future update to the engine. For those who would like to merge the fix directly into their source code, the following link can be used to grab the commit from GitHub for this fix.


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answered Dec 15 '14 at 06:46 PM

avatar image keyle Dec 16 '14 at 12:05 AM

Thanks Doug!

avatar image CombatJack Dec 20 '14 at 06:25 AM

I would highly recommend a 4.6.2 with just this change if possible. I'm glad I noticed this update to this issue, or I'd still be on 4.5.1 until whenever 4.7 comes out.

avatar image kurtrussellfanclub Jan 02 '15 at 07:38 AM

I agree with this -- thanks for the fix, but this is a project-buster

avatar image devlyn811 Jan 01 '15 at 06:53 PM

Thank you for this! :)

avatar image Dredok Jan 03 '15 at 08:12 PM

Are you sure this is the only change needed in 4.6.0 ??!?!?

I applied this and then I can not open my UMG widgets again!

Applying this commit in 4.6.0 will broke my UMG widgets !

I reverted the changes and everything works ...

avatar image Doug E ♦♦ STAFF Jan 05 '15 at 02:57 PM

Hey Dredok-

Just so I understand, when you say "everything works" after reverting the changes, does that mean you did not have the event dispatcher problem anymore? Also, did you try applying the commit using 4.6.1?

avatar image Dredok Jan 05 '15 at 04:10 PM

I mean, if you apply the commit changes on 4.6.0 or 4.6.1 it breaks my UMG widgets.

I had to revert the change. Everything works I mean event dispatcher problem is still there but at least UMG widgets work again.

So, at least with my widgets, applying the change in isolation on both 4.6.0 and 4.6.1 results in a broken editor

avatar image buscas31 Jan 05 '15 at 04:51 PM

I have the same problem! I have added the eventdispatcher ONE time in my level blueprint and my Editor version 4.6 crash one million times.....lol

In my case, i resolved this issue (or bug, i don´t know) on replace the actual map file with a backup auto generated map (thanks GOD and UNREAL!)

But, now i have fear to use the event dispatcher again :(

And, the actual link to the fix posted above, did not work :(

( https://github.com/EpicGames/UnrealEngine/commit/2600da3195f67bf7d7f0860c83961e3ddf268c1d )

avatar image Dredok Jan 05 '15 at 05:27 PM

as I said, I strongly discourage applying this commit isolate on 4.6.0 and 4.6.1 since it made my editor crash trying to open my UMG widgets :(

avatar image buscas31 Jan 05 '15 at 05:48 PM

Allright. I follow your sugestion, no doubt! And maybe i try to use player controller instead game mode for the actual (fail) eventdispatcher :)

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