Enumerations in Unreal Engine 4

EnumerationType.h

// Generally, developers in UE4 tend towards the following convention for enumerations:
UENUM( BlueprintType )
enum class ENoiseGeneratorCellularType : uint8
{
	NGCT_Natural			UMETA( DisplayName = "Natural" ),
	NGCT_Euclidean			UMETA( DisplayName = "Euclidean" ),
	NGCT_Manhattan			UMETA( DisplayName = "Manhattan" ),

	NGCT_Max			UMETA( Hidden )
};

// This works well enough, but it does require care in how you name enumeration values.
// Additionally, if you are serializing enumerations values into a proprietary file format or type.
//	For instance: I use text-based, non-binary JSON files for instance) so the numeric value of an enumeration types is necessary.
//
// To work around that, I tried this:
UENUM( BlueprintType )
enum ENoiseGeneratorCellularType
{
	NGCT_Natural			UMETA( DisplayName = "Natural" ),
	NGCT_Euclidean			UMETA( DisplayName = "Euclidean" ),
	NGCT_Manhattan			UMETA( DisplayName = "Manhattan" ),

	NGCT_Max			UMETA( Hidden )
};

// This will throw an error in any class/structure members that are specified as ENoiseGeneratorCellularType. Replace that with:
//	NOTE: Methods and local variables do not necessarily need to use this template.
TEnumAsByte< ENoiseGeneratorCellularType > CellularType;

// However, there is an even nicer way that still retains the standard enumeration support (to my knowledge) and allows you to use C#-styled enumeration values:
UENUM( BlueprintType )
namespace ENoiseGeneratorCellularType
{
    enum Type
    {
	Natural				UMETA( DisplayName = "Natural" ),
	Euclidean			UMETA( DisplayName = "Euclidean" ),
	Manhattan			UMETA( DisplayName = "Manhattan" ),

	Max				UMETA( Hidden )
    };
}

// Changing TEnumAsBute to:
TEnumAsByte< ENoiseGeneratorCellularType::Type > CellularType;

// From there on out, you can access enumeration values like this (without any global name conflicts):
CellularType = ENoiseGeneratorCellularType::Natural;

// Yay magic.

Same Here I got a lot of error when i try to create Enumerations

With 4.26 I used this one and it seems to work quite well.

UENUM( BlueprintType )
enum ENoiseGeneratorCellularType
{
	NGCT_Natural			UMETA( DisplayName = "Natural" ),
	NGCT_Euclidean			UMETA( DisplayName = "Euclidean" ),
	NGCT_Manhattan			UMETA( DisplayName = "Manhattan" ),

	NGCT_Max			UMETA( Hidden )
};
...
TEnumAsByte< ENoiseGeneratorCellularType > CellularType;

If you use enum ENoiseGeneratorCellularType : uint8 the build will fail with error : Missing '}' in 'Enum'.