# \[4.8 Promoted\] Extra parameters on BP callable functions not detected after hot-reload

**URL:** <https://forums.unrealengine.com/t/4-8-promoted-extra-parameters-on-bp-callable-functions-not-detected-after-hot-reload/315001>\
**Category:** Blueprint\
**Tags:** UE4-8, unreal-engine, bug-report, CPP, Blueprint, question, hot-reload\
**Created:** [April 14, 2015, 12:11pm UTC](https://forums.unrealengine.com/t/4-8-promoted-extra-parameters-on-bp-callable-functions-not-detected-after-hot-reload/315001 "2015-04-14T12:11:58Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![TommyBear](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@TommyBear](https://forums.unrealengine.com/u/TommyBear)\
**Post date:** [April 14, 2015, 12:11pm UTC](https://forums.unrealengine.com/t/4-8-promoted-extra-parameters-on-bp-callable-functions-not-detected-after-hot-reload/315001/1 "2015-04-14T12:11:58Z")

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When adding new parameters to functions on components which are “BlueprintCallable”, existing BPs reference this function will fail to compile until the node is manually removed and re-added.

Steps to reproduce:

- Start new project
- Place empty actor in the level
- Save the level and add a BP to this actor
- Do File | Add new c++ class
- Create new “ActorComponent” class with whatever name
- In either X-Code or Visual Studio add a new function “void TestFunction(float value)” + it’s implementation in the cpp
- Build
- Go back to the editor and observe the hot reload
- Click on actor in scene
- Add newly created c++ component onto this actor
- Edit the actor’s BP
- Add a call to the components test function
- Observe that the call function node has the correct “value” pin present
- Go back to XCode or Visual Studio
- Change function and implementation to be “void TestFunction(float value, float value2)”
- Build
- Go back to editor and wait for hot reload
- Notice after the hot reload that the call function node still only has one parameter pin (value)
- Expect to see “value2” pin appear
- Click compile on BP
- Note the compile error about the missing pin
- Pin still does not appear
- Delete the call function node
- Add it back
- Note the “value2” pin is now present

Tommy.

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**Author:** ![anonymous\_user\_2b03d27c](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_2b03d27c](https://forums.unrealengine.com/u/anonymous_user_2b03d27c)\
**Post date:** [April 17, 2015, 4:12pm UTC](https://forums.unrealengine.com/t/4-8-promoted-extra-parameters-on-bp-callable-functions-not-detected-after-hot-reload/315001/2 "2015-04-17T16:12:35Z")

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Hey TommyBear-

I was able to reproduce the BP node’s input pins not updating after a hot reload. This has been reported (UE-13981) for further investigation.

Cheers

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**Author:** ![rocifier](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@rocifier](https://forums.unrealengine.com/u/rocifier)\
**Post date:** [August 27, 2020, 10:30pm UTC](https://forums.unrealengine.com/t/4-8-promoted-extra-parameters-on-bp-callable-functions-not-detected-after-hot-reload/315001/3 "2020-08-27T22:30:43Z")

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Hi, this bug still occurs in 4.8.3 and furthermore is unfixable if it happens on custom events - using the Assign action generates the wrong class type on the event.

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**Author:** ![rocifier](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@rocifier](https://forums.unrealengine.com/u/rocifier)\
**Post date:** [August 27, 2020, 10:31pm UTC](https://forums.unrealengine.com/t/4-8-promoted-extra-parameters-on-bp-callable-functions-not-detected-after-hot-reload/315001/4 "2020-08-27T22:31:49Z")

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This bug is unrecoverable if it happens on custom events - using the Assign action generates the wrong class type on the event.