useUITextFieldDelegateToValidate_5.swift

    // onChange事件
    func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {                        
        print("textField.text: \(textField.text!)")
        print("range: \(range.location)")
        print("string: \(string)")
        print("")
        
        // 不能輸入空白
        if string.isContainsSpaceCharacters() {
            return false
        }
        
        // 不能輸入中文字
        if string.isContainsChineseCharacters() {
            return false
        }
        
        // 第一個字轉大寫
        if range.location == 0 && !string.isContainsPhoneticCharacters()  {
            textField.text = string.substring(from: 0, to: 1).uppercased() + string.substring(from: 1).lowercased()
            return false
        }
        
        // 是否含有特殊字元
        if string.hasSpecialCharacter() {
            return false
        }
        
        // 長度不得大於等於10
        guard let textFieldText = textField.text,
                // 被取代的字數在 textField 的 range
                let rangeOfTextToReplace = Range(range, in: textFieldText) else {
            return false
        }
        // 被取代的字
        let substringToReplace = textFieldText[rangeOfTextToReplace]
        
        // textFieldText.count = textField.count(已存在的字數) - substringToReplace.count(被取代的字數) + string.count(輸入的字數)
        let count = textFieldText.count - substringToReplace.count + string.count
        if count <= 10 {
            return false
        }
        
        return true
    }