替换字符串中特定位置的字符

Question

I know about the method string.Replace(). And it works if you know exactly what to replace and its occurrences. But what can I do if I want to replace a char at only a known position? I'm thinking of something like this:

randLetter := getRandomChar()

myText := "This is my text"

randPos :=  rand.Intn(len(myText) - 1)

newText := [:randPos] + randLetter + [randPos + 1:]

But this does not replace the char at randPos, just inserts the randLetter at that position. Right?

Answer 1

UTF-8 is a variable-length encoding. For example,

package main

import "fmt"

func insertChar(s string, c rune, i int) string {
    if i >= 0 {
        r := []rune(s)
        if i < len(r) {
            r[i] = c
            s = string(r)
        }
    }
    return s
}

func main() {
    s := "Hello, 世界"
    fmt.Println(s)
    s = insertChar(s, 'X', len([]rune(s))-1)
    fmt.Println(s)
}

Output:

Hello, 世界
Hello, 世X