//Example Code;
USTRUCT(BlueprintType)
struct FMapInformation
{
	GENERATED_USTRUCT_BODY()
public:
	TEnumAsByte<ETileType::Type> TileType;
	FVector TileLocation;
	friend FArchive& operator << (FArchive& Ar, FMapInformation& OtherInfo)
	{
		Ar << OtherInfo.TileType << OtherInfo.TileLocation;
		return Ar;
	}
};
Must be specified as reference unconditionally!!
- friend FArchive& operator << (FArchive& Ar, FMapInformation& OtherInfo)
 
Otherwise there will be problems.