How to check if there is a special character in string or if a character is a special character in GoLang - string

Question

After reading a string from the input, I need to check if there is a special character in it

Answer 1

You can use strings.ContainsAny to see if a rune exists:
package main
import (
"fmt"
"strings"
)
func main() {
fmt.Println(strings.ContainsAny("Hello World", ",|"))
fmt.Println(strings.ContainsAny("Hello, World", ",|"))
fmt.Println(strings.ContainsAny("Hello|World", ",|"))
}
Or if you want to check if there are only ASCII characters, you can use strings.IndexFunc:
package main
import (
"fmt"
"strings"
)
func main() {
f := func(r rune) bool {
return r < 'A' || r > 'z'
}
if strings.IndexFunc("HelloWorld", f) != -1 {
fmt.Println("Found special char")
}
if strings.IndexFunc("Hello World", f) != -1 {
fmt.Println("Found special char")
}
}

Answer 2

Depending on your definition of special character, the simplest solution would probably to do a for range loop on your string (which yield runes instead of bytes), and for each rune check if it is in your list of allowed/forbidden runes.
See Strings, bytes, runes and characters in Go for more about the relations between string, bytes and runes.
Playground example
package main
var allowed = []rune{'a','b','c','d','e','f','g'}
func haveSpecial(input string) bool {
for _, char := range input {
found := false
for _, c := range allowed {
if c == char {
found = true
break
}
}
if !found {
return true
}
}
return false
}
func main() {
cases := []string{
"abcdef",
"abc$€f",
}
for _, input := range cases {
if haveSpecial(input) {
println(input + ": NOK")
} else {
println(input + ": OK")
}
}
}

Answer 3

You want to use the unicode package, which has a nice function to check for symbols.
https://golang.org/pkg/unicode/#IsSymbol
package main
import (
"fmt"
"unicode"
)
func hasSymbol(str string) bool {
for _, letter := range str {
if unicode.IsSymbol(letter) {
return true
}
}
return false
}
func main() {
var strs = []string {
"A quick brown fox",
"A+quick_brown<fox",
}
for _, str := range strs {
if hasSymbol(str) {
fmt.Printf("String '%v' contains symbols.\n", str)
} else {
fmt.Printf("String '%v' did not contain symbols.\n", str)
}
}
}
This will provide the following output:
String 'A quick brown fox' did not contain symbols.
String 'A+quick_brown<fox' contains symbols.

Answer 4

I ended up doing something like this
alphabet := "abcdefghijklmnopqrstuvwxyz"
alphabetSplit := strings.Split(alphabet, "")
inputLetters := strings.Split(input, "")
for index, value := range inputLetters {
special:=1
for _, char :=range alphabetSplit{
if char == value {
special = 0
break
}
}
It might have anything wrong because since I used it to something specific i had to edit to post it here