Enumerator in Go

1. Use the iota to Represent enums in Go
2. Use the iota to Auto-Increment Number Declaration in Go
3. Use the iota to Create Common Behavior in Go

An enum (short for enumerator) is used to design complicated groupings of constants with meaningful names but simple and distinct values.

In Go, there is no enum data type. We use the identifier iota that is predefined, and enums are not tightly typed.

Use the iota to Represent enums in Go

iota is a constant identifier that can simplify auto-increment number declarations. It denotes a zero-based integer constant.

The iota keyword represents the numeric constants 0, 1, 2,.... The term const appears in the source code resets to 0 and increases with each const specification.

package main

import "fmt"

const (
	a = iota
	b = iota
	c = iota
)

func main() {
	fmt.Println(a, b, c)
}

Output:

0 1 2

Use the iota to Auto-Increment Number Declaration in Go

Using this method, you can avoid placing sequential iota in front of each constant.

package main

import "fmt"

const (
	a = iota
	b
	c
)

func main() {
	fmt.Println(a, b, c)
}

Output:

0 1 2

Use the iota to Create Common Behavior in Go

We define a simple enum named Direction, which has four potential values: "east", "west", "north" and "south".

package main

import "fmt"

type Direction int

const (
	East = iota + 1
	West
	North
	South
)

// Giving the type a String method to create common behavior
func (d Direction) String() string {
	return [...]string{"East", "West", "North", "South"}[d-1]
}

// Giving the type an EnumIndex function allows you to provide common behavior.
func (d Direction) EnumIndex() int {
	return int(d)
}

func main() {
	var d Direction = West
	fmt.Println(d)
	fmt.Println(d.String())
	fmt.Println(d.EnumIndex())
}

Output:

West
West
2