Golang : Increment string example

Problem:

You need to create "copies" of a file, prevent user from overwriting files accidentally or need duplicate database content which has unique titles or slugs. Having increment string function is helpful in this kind of situation. How to do that?

Solution:

Increments a string by appending a number to it or increasing the number.

Below is a function to increment the string value that you can use or adapt to your own Golang code.

 package main

 import (
  "fmt"
  "os"
  "strconv"
  "strings"
 )

 func incrementString(str string, separator string, first int) string {

  // set default values
  // see https://www.socketloop.com/tutorials/golang-proper-way-to-set-function-argument-default-value

  if separator == "" {
 separator = "_"
  }

  if first == 0 || first < 0 {
 first = 1
  }

  // test to see if str already has integer suffix(ends with _#)
  test := strings.SplitN(str, separator, 2)

  if len(test) >= 2 {
 // increase file counter by 1
 i, err := strconv.Atoi(test[1])

 if err != nil {
 fmt.Println(err)
 os.Exit(1)
 }

 increased := i + first
 return test[0] + separator + strconv.Itoa(increased)
  } else {
 return str + separator + strconv.Itoa(first)
  }
 }

 func main() {

  result := incrementString("file", "_", 0)
  fmt.Println(result)

  result = incrementString("file", "-", 2)
  fmt.Println(result)

  // increase by 1
  result = incrementString("file_2", "", 1)
  fmt.Println(result)

  // increase by 2
  result = incrementString("file_2", "", 2)
  fmt.Println(result)

  // increase by 100
  result = incrementString("file_3", "", 100)
  fmt.Println(result)

  // change separator to # sign
  result = incrementString("imagefiles", "#", 10)
  fmt.Println(result)

  // will NOT accept negative number. will change to default value of 1
  result = incrementString("imagefiles", "#", -99)
  fmt.Println(result)

 }

Output:

file_1

file-2

file_3

file_4

file_103

imagefiles#10

imagefiles#1

Happy coding!

References:

https://golang.org/pkg/strings/#SplitN