Controlling Case

• There are a lot of practical tasks where the modification of case is the most common approach. Let's pick a few of these:

  • Case-insensitive comparison
  • Beginning the sentence with an automatic first capital
  • Camel-case to snake-case conversion

For these purposes, the strings package offers functions ToLower, ToUpper, ToTitle, and Title.

How to do it...

Create the main.go file with the following content:

package main

import (
    "fmt"
    "strings"
    "unicode"
)

const email = "ExamPle@domain.com"
const name = "isaac newton"
const upc = "upc"
const i = "i"

const snakeCase = "first_name"

func main() {

    // For comparing the user input
    // sometimes it is better to
    // compare the input in a same
    // case.
    input := "Example@domain.com"
    input = strings.ToLower(input)
    emailToCompare := strings.ToLower(email)
    matches := input == emailToCompare
    fmt.Printf("Email matches: %t\n", matches)

    upcCode := strings.ToUpper(upc)
    fmt.Println("UPPER case: " + upcCode)

    // This digraph has different upper case and
    // title case.
    str := "dz"
    fmt.Printf("%s in upper: %s and title: %s \n", str,
        strings.ToUpper(str), strings.ToTitle(str))

    // Use of XXXSpecial function
    title := strings.ToTitle(i)
    titleTurk := strings.ToTitleSpecial(unicode.TurkishCase, i)
    if title != titleTurk {
        fmt.Printf("ToTitle is defferent: %#U vs. %#U \n",
            title[0], []rune(titleTurk)[0])
    }

    // In some cases the input
    // needs to be corrected in case.
    correctNameCase := strings.Title(name)
    fmt.Println("Corrected name: " + correctNameCase)

    // Converting the snake case
    // to camel case with use of
    // Title and ToLower functions.
    firstNameCamel := toCamelCase(snakeCase)
    fmt.Println("Camel case: " + firstNameCamel)

}

func toCamelCase(input string) string {
    titleSpace := strings.Title(strings.Replace(input, "_", " ", -1))
    camel := strings.Replace(titleSpace, " ", "", -1)
    return strings.ToLower(camel[:1]) + camel[1:]
}

output:

sangam:golang-daily sangam$ go run main.go
Email matches: true
UPPER case: UPC
dz in upper: DZ and title: Dz 
ToTitle is defferent: U+0049 'I' vs. U+0130 'İ' 
Corrected name: Isaac Newton
Camel case: firstName
sangam:golang-daily sangam$

How it works...

• Note that the title-case mapping in Unicode differs from the uppercase mapping. The difference is that the number of characters requires special handling. These are mainly ligatures and digraphs such as fl, dz, and lj, plus a number of polytonic Greek characters. For example, U+01C7 (LJ) maps to U+01C8 (Lj) rather than to U+01C9 (lj).