Iterating over UENUM with TEnumRange

I've always wanted to iterate over UENUM values but never known how, until Wouter Weynants told me this tip.

Before

Our simple enum example just lists a few animal types.

UENUM()
enum class EAnimal : uint8
{
	Cat,
	Dog,
	Elephant
};

Making our Enum iteration-friendly

In order to make our enum iterate-able, we need to use one of three possible macros that Unreal provides:

• ENUM_RANGE_BY_COUNT
• ENUM_RANGE_BY_FIRST_AND_LAST
• ENUM_RANGE_BY_VALUES

By Count

There are a few different macros that we can use to enable iteration over a UENUM. We'll start with what might be the simplest, ENUM_RANGE_BY_COUNT and then show you how to iterate.

First we want to add a new value to the end of our enum. It can be called anything but Count is a good standard to use.

You can hide this value so it doesn't show up in the editor by marking it with UMETA(Hidden)

Finally we need to add ENUM_RANGE_BY_COUNT and include the name of the enum and the final value we are using to store the size or count of our enum.

UENUM()
enum class EAnimal : uint8
{
	Cat,
	Dog,
	Elephant,
	Count UMETA(Hidden)
};
ENUM_RANGE_BY_COUNT(EAnimal, EAnimal::Count);

By First and Last

Unreal also has ENUM_RANGE_BY_FIRST_AND_LAST that can be useful if you don't want to add an extra Count value to your enum. As before, we add the macro after our enum definition, but in this case, we pass in the first and last entries from the enum.

UENUM()
enum class EMilkshake : uint8
{
	Chocolate,
	Vanilla,
	Strawberry,
	Blueberry
};
ENUM_RANGE_BY_FIRST_AND_LAST(EMilkshake, EMilkshake::Chocolate, EMilkshake::Blueberry);

By Values

Useful for defining iteration over an enum with a non-contiguous range of values. We pass in every value in the enum, in order.

enum class ERandomValuesThing : uint8
{
	First  = 2,
	Second = 3,
	Third  = 5,
 	Fourth = 7,
 	Fifth  = 11
};

ENUM_RANGE_BY_VALUES(ERandomValuesThing, ERandomValuesThing::First, ERandomValuesThing::Second, ERandomValuesThing::Third, ERandomValuesThing::Fourth, ERandomValuesThing::Fifth)

Iterating over the enum

No matter which ENUM_RANGE_BY... macro we used, iteration is the same:

for (EAnimal Animal : TEnumRange<EAnimal>())
{

}