support lambda functions in delegates

General Feedback & Requests
1

I’m looking at timeline delegates and it would be nice to support lambda functions for delegates.

2

You can actually use lambdas already with UE4 delegates, as long as you don’t capture variables with your lambda. Here is an example from some Slate UI.


	
SNew(SImage)
	.Image( FEditorStyle::GetBrush("EditorLiveStreaming.BroadcastButton") )
	.ColorAndOpacity_Static( ] 
	{ 
		FSlateColor Color = FLinearColor( 1.0f, 1.0f, 1.0f, FMath::MakePulsatingValue( FSlateApplication::Get().GetCurrentTime(), 2.0f ) );
		return Color;
	} )

For timelines, you would use syntax like:


	
MyDelegate = FOnTimelineEvent::CreateStatic( ] { DoSomething(); } );

In 4.6 we will have support for stateful lambdas as well, by using the new “FMyDelegate::CreateLambda()” functions that we’ve added. Hope that helps!

–Mike

3

good news ! thanks Mike :slight_smile:

4

lambda(lambda) :slight_smile:

5

Awesome! Thanks Mike!

6

In the upcoming Unreal Engine 4.6 we’ve added even better support for lambdas with delegates. You can use the new “CreateLambda” and “BindLambda” functions to bind your delegate to a lambda that captures local variables. https://github.com/EpicGames/UnrealEngine/commit/1d84d219d2e5c3082d3d188c13050db5c18cd682

–Mike

7

cool !

is this change in some 4.5 tag branches? or only in main branch?

8

Just in “master” branch on GitHub for now, which is the super-early version of UE 4.6. But you could manually merge the changes over to your branch if you really wanted to of course.

–Mike