11. Constants

Can not change me

What are constants?

A const declaration defines named values that look syntactically like variables but whose value is constant.Instead of the var keyword, we use the const keyword.A value must be assigned while declaring constants.Constants only exists during compile time!

Declaring constants

Constants are declared using const keyword.

main.go

const pi = 3.14

Constant Block

Similar to variable block, we can also have constant block.

main.go

const (
	pi         = 3.14
	daysInWeek = 7
)

IOTA

iota can be used to create enumerated constants. It is also called as constant generator.

main.go

const (
	Sunday int = iota
)

func main() {
	fmt.Println(Sunday)
}

Benefits of using iota is that it will increment itself for next const declaration in same const block.

main.go

const (
	Monday int = iota + 1
	Tuesday
	Wednesday
	Thursday
	Friday
	Saturday
	Sunday
)

func main() {
	fmt.Println(Monday, Tuesday, Wednesday, Thursday, 
	Friday, Saturday, Sunday)
}
// output : 1 2 3 4 5 6 7

From the Docs

Effective Go - The Go Programming Languagegolang

Constants

Blog Posts

Constants - The Go Programming Languagegolang

IotaGitHub

Go by Example: Constants and iotadlintw.github.io

iota: Elegant Constants in Golang - Blog | SpliceBlog | Splice