How to check if my string matches with regex - Swift 3

I searched everywhere but it does not correspond to my
request.
How to check if a string matches with a regex ?
I
don't want to know if my string contains caracters or which
they are but I want to do a function which returns true or
false : does this string "abcdefgh" matches with
"[a-z]".

I can do it in
PHP, JS but apparently in Swift all people want only to know which caracters matche.
^^

Regards,