Using Enum Value In Property Meta Data Does Not Compile

Development Programming & Scripting
1

So I am trying to set a key value pair in a UPROPERTY Metadata section, where the value is a enumeration-value:

UPROPERTY(BlueprintReadOnly, Category = "Output", Meta = (Unit = EUnits::Percentage))
	float ChargingStatus = 0.f;

The enum is defined like this:

UENUM()
enum class EUnits : uint8 {
	Percentage,
	Seconds
};

This code does not compile, I get this error:

Error C:/Workspaces/Unreal Engine 4/TheSpaceGame/Source/TheSpaceGame/GaussCanonModule.h(45) : Error: Missing ‘)’ in Variable declaration specifier

(line 45 is the UPROPERTY(BlueprintReadOn… line)

which is not very helpfull. If I substiute the Enum Value with an integer literal for example it works. Does that mean that enums are not suppoerted in the meta data of a property? If so, is there a workaround, or will I just have to use some defines maybe to get a literal value in there?

I’m looking forward to your help!

EDIT:

And it gets better. Defines don’t work either (maybe a macro in a macro causes problems?) It does compile but, when I use

it2->GetINTMetaData("Unit")

It just returns 0. I am now at the stage, where I put in integer literals, which defeats the whole point of enumerations. There has to be a better way.

2

Well it’s been some time now … I hoped that someone from Epic would have a look at this, since the community doesn’t seem to know much about this.

3

Out of curiosity, have you tried using removing the “class” modifier from your enum (thus making it effectively just an int in disguise)? Enum Classes are a C++11 thing that enforce type safety so I could see that causing issues.

4

Out of curiosity, have you tried using removing the “class” modifier from your enum (thus making it effectively just an int in disguise)? Enum Classes are a C++11 thing that enforce type safety so I could see that causing issues.

You are right, it works like this now:

UENUM()
enum EUnits {
	None = 0,
	Percentage = 1,
	Seconds = 2
};

I then had to change all the enum members that I had to TEnumAsBytey but thats not a big deal.

5

Although now I found this under the coding standards:

Enum classes should always be used as a replacement for old-style namespaced enums, both for regular enums and UENUMs.

These are also supported as UPROPERTYs, as long they are based on uint8 - this replaces the old TEnumAsByte<> workaround:

So my workaround cannot be intended by Epic. I suspect a bug.