This is possible, but is a bit hazardous, and I would not recommend doing it for anything at all sensitive.
A good example of not requiring signups is mailinator.com, which relies on randomness instead. When you use the site, you can pick an "unguessable" name to use as an email address, such as lbpxlm4ChXVH6Utv9jUvxR0kB2nNHA@mailinator.com
, and you can simply use it as you like. Bear in mind though that this relies on luck: there is nothing whatsoever preventing anyone else accessing the account beyond not being able to guess the string you use. For example log in using an easily guessed name like Julia
, and you'll see someone else's email!
While it's nice to be able to do this, note that it relies on the user remembering their login string accurately too – there isn't really a viable way of doing the equivalent of a password reset.
This is also not too far from what is referred to as "magic links" for logins, which is an alternative to id and password.
None of this is specific to Swift – you could implement this in any language.