GO does not natively support an enum keyword; however, an enum-like syntax can be implemented using the help of iota.
What is iota?
iota is an identifier that auto increments constants.
In the following code, the constant number is manually incremented:
1
2
3
4
5
| const (
ZERO = 0
ONE = 1
TWO = 2
)
|
however, it can be simplified to:
1
2
3
4
5
| const (
ZERO = iota // 0
ONE // 1
TWO // 2
)
|
If desired, the iota keyword can be used on each line:
1
2
3
4
5
| const (
ZERO = iota // 0
ONE = iota // 1
TWO = iota // 2
)
|
If a const keyword is used again, the iota will reset to 0.
1
2
3
4
5
6
7
8
9
10
11
| const (
ZERO = iota // 0
ONE // 1
TWO // 2
)
const (
ZEROAGAIN = iota // 0
ONEAGAIN // 1
TWOAGAIN // 2
)
|
Implementing an enum in GO
Using a combination of iota, int and const, the concept of an enum can be applied.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
| package main
import "fmt"
type PizzaSize int
const (
SMALL PizzaSize = iota + 1 // 1
MEDIUM // 2
LARGE // 3
)
func (s PizzaSize) String() string {
return [...]string{"Small", "Medium", "Large"}[s-1]
}
func (s PizzaSize) Index() int {
return int(s)
}
func main() {
size := SMALL
fmt.Println(size) // Print : Small
fmt.Println(size.String()) // Print : Small
fmt.Println(size.Index()) // Print : 1
}
|