Golang : Count number of runes in string
This just a note for myself and perhaps it can be useful to you as well.
To count a length(size) of a string, typically a programmer will just settle for the the builtin.Len() function. However, when dealing with strings with utf8 characters. Please use the utf8.RuneCountInString() function. See the code below to know why :
package main
import (
"fmt"
"unicode/utf8"
)
func main() {
str := "abc"
fmt.Printf("Length %s with len() is %d\n", str, len(str)) // correct
unicodeStr := "fuß"
fmt.Printf("Length %s with len() is %d\n", unicodeStr, len(unicodeStr)) // incorrect
fmt.Printf("Length %s with utf8.RuneCountInString() is %d\n", unicodeStr, utf8.RuneCountInString(unicodeStr)) // correct
unicodeStr2 := "你好"
fmt.Printf("Length %s with len() is %d\n", unicodeStr2, len(unicodeStr2)) // incorrect
fmt.Printf("Length %s with utf8.RuneCountInString() is %d\n", unicodeStr2, utf8.RuneCountInString(unicodeStr2)) // correct
}
Output :
Length abc with len() is 3
Length fuß with len() is 4
Length fuß with utf8.RuneCountInString() is 3
Length 你好 with len() is 6
Length 你好 with utf8.RuneCountInString() is 2
See also : Golang : convert rune to integer value
By Adam Ng
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