1、默认样式
case `default` = 0 // Default type for the current input method.
2、ASCII 码键盘
case asciiCapable = 1 // Displays a keyboard which can enter ASCII characters
3、数字和标点符号
case numbersAndPunctuation = 2 // Numbers and assorted punctuation.
4、URL键盘
case URL = 3 // A type optimized for URL entry (shows . / .com prominently).
5、数字键盘
case numberPad = 4 // A number pad with locale-appropriate digits (0-9, ۰-۹, ०-९, etc.). Suitable for PIN entry.
6、电话号码键盘
case phonePad = 5 // A phone pad (1-9, *, 0, #, with letters under the numbers).
7、姓名电话号码键盘
case namePhonePad = 6 // A type optimized for entering a person's name or phone number.
8、电子邮件键盘
case emailAddress = 7 // A type optimized for multiple email address entry (shows space @ . prominently).
9、带小数点的数字键盘
@available(iOS 4.1, *)
case decimalPad = 8 // A number pad with a decimal point.
10、Twitter 键盘
@available(iOS 5.0, *)
case twitter = 9 // A type optimized for twitter text entry (easy access to @ #)
11、Web 键盘
相对于 URL 键盘，突出空格
@available(iOS 7.0, *)
case webSearch = 10 // A default keyboard type with URL-oriented addition (shows space . prominently).
12、ASCII 数字键盘
@available(iOS 10.0, *)
case asciiCapableNumberPad = 11 // A number pad (0-9) that will always be ASCII digits.
