# Implementing interface bug 4.9 release

**URL:** <https://forums.unrealengine.com/t/implementing-interface-bug-4-9-release/330293>\
**Category:** UI\
**Tags:** interface, restart, unreal-engine, bug-report, Blueprint, question\
**Created:** [August 29, 2015, 1:30pm UTC](https://forums.unrealengine.com/t/implementing-interface-bug-4-9-release/330293 "2015-08-29T13:30:00Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![anonymous\_user\_fbe5155f](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_fbe5155f](https://forums.unrealengine.com/u/anonymous_user_fbe5155f)\
**Post date:** [August 29, 2015, 1:30pm UTC](https://forums.unrealengine.com/t/implementing-interface-bug-4-9-release/330293/1 "2015-08-29T13:30:00Z")

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Steps to reproduce

- Create interface with A method
- Implement in a blueprint
- Observe function automatically implemented
- Remove implementation of interface (via ‘x’ icon)
- Accept “transfer interface functions to blueprint”
- Try reimplement interface

expected: it would re-implement the interface.

actual: nothing happens.

This happens since you already have a method signature fitting the interface… So even though your actor fits the signature before interface implementation perfectly, your actor can’t be marked as implementing the interface.

Also, if you were to update your interface and add a second method, that interface cannot be implemented until the blueprint function is removed (OR RENAMED).

Suggesting: display a friendly message “conflicting existing functions in blueprint with interface implementation”, or actually move the blueprint function as interface implementation if the signature matches.

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**Author:** ![anonymous\_user\_b9532c9a](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_b9532c9a](https://forums.unrealengine.com/u/anonymous_user_b9532c9a)\
**Post date:** [August 31, 2015, 2:46pm UTC](https://forums.unrealengine.com/t/implementing-interface-bug-4-9-release/330293/2 "2015-08-31T14:46:19Z")

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Hi ,

Does this occur in a clean, blank project with no additional content or is it limited to one project? Are you adding any specific functionality to the interface or does it occur by just adding a single function with no functionality to the interface? Do you get any warnings or errors?

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<div class="post-metadata">

**Author:** ![anonymous\_user\_fbe5155f](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_fbe5155f](https://forums.unrealengine.com/u/anonymous_user_fbe5155f)\
**Post date:** [September 1, 2015, 12:04am UTC](https://forums.unrealengine.com/t/implementing-interface-bug-4-9-release/330293/3 "2015-09-01T00:04:52Z")

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Hi ,

yes I could reproduce it, however I forgot to mention a step

When removing the blueprint’s implementation of the interface (via ‘x’ icon), I chose to _keep the interface function_.

I will completely rephrase the above bug because I’ve found more information.

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<div class="post-metadata">

**Author:** ![anonymous\_user\_fbe5155f](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_fbe5155f](https://forums.unrealengine.com/u/anonymous_user_fbe5155f)\
**Post date:** [September 1, 2015, 12:09am UTC](https://forums.unrealengine.com/t/implementing-interface-bug-4-9-release/330293/4 "2015-09-01T00:09:59Z")

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Ticket rewritten, clearer and tested with 4.9 release. HTH.

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<div class="post-metadata">

**Author:** ![anonymous\_user\_b9532c9a](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_b9532c9a](https://forums.unrealengine.com/u/anonymous_user_b9532c9a)\
**Post date:** [September 1, 2015, 2:49pm UTC](https://forums.unrealengine.com/t/implementing-interface-bug-4-9-release/330293/5 "2015-09-01T14:49:43Z")

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Hi ,

I was able to reproduce this and have entered a bug report, UE-20596, to be assessed by the development staff.