With swift determination letter string contains

/ * String to determine that String * /
let characterset = CharacterSet(charactersIn: string)
let stringContain = string.rangeOfCharacter(from: characterset)
if stringContain != nil{
/ * Include * /
}

/* 或 */
let stringContain1 = string.rangeOfCharacter(from: NSCharacterSet.letters)
if stringContain1 != nil{
/* 包含 */
}