iOS 键盘最上方显示验证码

先看一下效果图：

官方文档：

// The textContentType property is to provide the keyboard with extra information about the semantic intent of the text document.
@property(null_unspecified,nonatomic,copy) UITextContentType textContentType API_AVAILABLE(ios(10.0)); // default is nil

直接上代码：

if (@available(iOS 10.0, *)) {
    //Xcode 10 适配
    self.codeField.textContentType = UITextContentTypeOneTimeCode; 
}

xib设置：