如何在字符串的特定位置找到准确的字符

Question

I have the following string:

absoloute-power

As you can see, there is a "-" at position number 10 in the string. How do I write the go code to validate if the 10th position of any given string has a "-" in the string?

Answer 1

In Go, string character values are Unicode characters encoded in UTF-8. UTF-8 is a variable-length encoding which uses one to four bytes per character.

For your example:

package main

import (
    "fmt"
    "unicode/utf8"
)

func is10Hyphen(s string) bool {
    for n := 1; len(s) > 0; n++ {
        r, size := utf8.DecodeRuneInString(s)
        if r == utf8.RuneError && (size == 0 || size == 1) {
            return false
        }
        if n == 10 {
            return r == '-'
        }
        s = s[size:]
    }
    return false
}

func main() {
    s := "absoloute-power"
    fmt.Println(is10Hyphen(s))
    s = "absoloute+power"
    fmt.Println(is10Hyphen(s))
    s = "absoloute"
    fmt.Println(is10Hyphen(s))
}

Playground: https://play.golang.org/p/h9rMQWWAdvb

Output:

true
false
false

---

If you are willing to consider encountering the Unicode replacement character an error, then for your example:

func is10Hyphen(s string) bool {
    n := 0
    for _, r := range s {
        if r == utf8.RuneError {
            return false
        }
        n++
        if n == 10 {
            return r == '-'
        }
    }
    return false
}

Playground: https://play.golang.org/p/SHbPAnldTyw

Answer 2

You could use a rune-array:

text := "ifthisisyourstring"
chars := []rune(text)
if chars[0] == '1' {
    // is true
}

Answer 3

As string is an array in fact, you can access the 10th position directly.Of course, need to avoid "out of range " error. For the case of the non-ascii encoding, converting it to a rune array

package main

import (
  "fmt"
)

func main() {
  fmt.Println(Check("213123-dasdas"))
  fmt.Println(Check("213123sdas"))
  fmt.Println(Check("213123das-das"))
  fmt.Println(Check("213123dasda-s"))
  fmt.Println(Check("---------2----------"))
}

func Check(ss string) bool {
  r = []rune(ss)
  if len(r) < 10 {
    return false
  }
  return ss[r] == '-'
}