Swift 5
UIAccessibility.post(notification: .announcement, argument: "your text")
There does not seem to be a queue (still, on iOS 13). If you post your announcement immediately after a user action, such as a button tap, it may get swallowed by the button's automatic voice-over announcement. In this case you should post your announcement after a suitable delay (as mentioned here). If that delay is too short, your announcement might cut into the button's announcement.
AVSpeechUtterance
will speak the text to all users, UIAccessibility.post
only to those that have selected Voice-Over in their accessibility settings, f.i. because they are visually impaired.