如何在MFMailComposeController中实现类似于电子邮件文本字段的UITextField

In MFMailComposeController, once we start typing, the list of email addresses is shown. Once we select, the TextField displays the name of the user with a small Oval background. Then we can continue typing. If we want to delete it, then pressing backspace selects the oval background and on second backspace the email address is deleted. How can this be implemented., once we start typin