Question about declaration of classes, structs, and enums in C++

Development Programming & Scripting C++
1

I’ve been trying to follow the coding standards of Unreal, and I’m curious about a few things. I’ve been declaring structs and classes with a specified module API. What is the benefit of doing this? Is there any difference if I just leave it out?



USTRUCT(BlueprintType)
struct STEAMMATCHMAKING_API FSteamSessionSettings
{
GENERATED_BODY()

// ...
};

I wanted to follow the pattern above and declare an enum with module API, but the compile always fails. Is there a way (or a reason) to declare an enum with a module API? I know I can just remove the module API and it would work, but I’m curious why.



UENUM()
enum class STEAMMATCHMAKING_API ESteamReservationResponse : uint8
{
     // Getting compile error : Missing '{' in 'Enum'
};

Interestingly enough, Epic usually declares enums like this:



UENUM()
namespace EPartyReservationResult
{
     enum Type
     {
          // ...
     };
}
2

IIRC you don’t need to export enums.

The namespaced enums are a thing of the past really, and IMO should be avoided because then you are forced to use TEnumAsByte when using it with reflection, which can be pretty annoying.

3

If you have in C++ one Editor module using types from a Kismet module which uses types from a Runtime module… You must export dependency types using the module name macro, because each module code in that case is going to land in a different DLL.

If the only target of that type is to be exposed to Blueprints VM, export macro is not needed. Just UTHING() is already enough.