返回 const 指针会在虚幻引擎中引发编译错误？

Question

I am not terribly great at C++ so I am sorry in advance if this is just a silly mistake. I was trying to expose the XMLParser to blueprints in Unreal Engine

Using VS, the code doesn't show any compile errors inline. (ie no red lines anywhere) However, when I try to compile, I get the following error:

Unrecognized type 'FXmlNode' - type must be a UCLASS, USTRUCT or UENUM

The line of code in question:

UFUNCTION(BlueprintCallable)
        const FXmlNode* GetRoot();

I updated the Build.cs with the XMLParser module and can access the functions inside of the various XML classes. However, I find it odd that the compiler doesn't recognize it. Does anyone know what might be causing this?

Any help would be greatly appreciated.

Answer 1

The solution to this was rather a simple once I actually thought about it a little bit. The XmlNode class was not a UCLASS type and I can't return a non-U* type inside of Blueprints which was an issue. (Hence why the error makes sense now)

Instead I created another wrapper class for the XmlNode class itself and made it a UCLASS type. From there it was rather easy to wrap the XmlNode class since it mainly was returning Strings and other node references.

Answer 2

Reflection system in UE4 does not support pointers to USTRUCTS. You can use it in your code, but it's not possible to expose USTRUCT pointers to Blueprints, you must return struct either by value or const reference