UPDATE
From iOS 12 Apple will allow the support to read One Time Code(OTP - One Time Password) which you will get in the iPhone device.
iOS supports Password AutoFill on UITextField, UITextView, and any custom view that adopts the UITextInput protocol. System keyboard set the textContentType on it to .oneTimeCode
1) Using Code
singleFactorCodeTextField.textContentType = .oneTimeCode
2) Using Storyboard/XIB
Select UITextField
/UITextView
in storyboard/XIB
click Click on Attribute
inspector. Go to text input trait, click to Content type and select
one time code and done.
The operating system will detect verification codes from Messages automatically with this UITextContentType
set.
Warning
If you use a custom input view for a security code input text field,
iOS cannot display the necessary AutoFill UI.
For more information, you can check it on the Apple developer oneTimeCode
And also review WWDC 2018 Session 204 - Automatic Strong Passwords and Security Code AutoFill and jump to 24:28 for automatic pre-fill the OTP.