Alerting the user as to a particular situation is done with, well, an alert box.

There are three fundamental steps to setting up an alert box:

  • defining the alert
  • adding an action request, and
  • presenting the alert to the user.

This is shown in the code which follows.

// Step one: create the alert and specify basic information:
let alert = UIAlertController(
    title:          "Title for the alert box",
    message:        "Message outlining the nature of the alert",
    preferredStyle: .alert)
// Step two: add instructions to the user. Note that if this is
// omitted, the box will still display but it will not be possible to
// dismiss it by tapping outside the box.
alert.addAction(
    UIAlertAction(
        title:          "Remedial action to be taken",
        style:          .default,
        handler:        nil) )
// Step three: present the alert and await the user's response.
present( alert, animated: true, completion: nil )