Range: Iterating Over Collections

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Range: Iterating Over Collections

The range keyword provides a way to iterate over elements of slices, arrays, maps, and strings. For slices and arrays, it returns the index and value. For maps, it returns the key and value. For strings, it returns the byte index and the Unicode code point. If you only need one value, you can ignore the other with the blank identifier underscore.

snippet.go
go
package main
 
import "fmt"
 
func main() {
    fruits := []string{"apple", "banana", "cherry"}
 
    for index, fruit := range fruits {
        fmt.Printf("%d: %s\n", index, fruit)
    }
 
    capitals := map[string]string{
        "Germany": "Berlin",
        "France":  "Paris",
    }
 
    for country, capital := range capitals {
        fmt.Printf("%s -> %s\n", country, capital)
    }
 
    for i, char := range "Hello" {
        fmt.Printf("%d: %c\n", i, char)
    }
}

Breakdown

for index, fruit := range fruits

Iterates slice, index=0,1,2; fruit="apple","banana","cherry"

for country, capital := range capitals

Iterates map, order is random each run

for i, char := range "Hello"

Iterates string bytes, i=0,1,2,3,4; char='H','e','l','l','o'

_ , fruit := range fruits

Blank identifier ignores the index

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Range: Iterating Over Collections

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