Sending text messages from your iOS app in Swift using MFMessageComposeViewController

The iOS app can display a pre-composed message for the user to send using MFMessageComposeViewController. The user's phone number is not required, but if programmatically sending an SMS from a different phone number is desired, Swift and Twilio can be used. To get started, Xcode 9 and Swift 4 are needed, and a new project should be created with the "Single View App" option. A ViewController class must conform to MFMessageComposeViewControllerDelegate protocol and add a stub method. A function called displayMessageInterface is added to present the message composition interface with a pre-populated body and recipient number. The function is then wired up to a button in Main.storyboard, allowing it to be executed when pressed.