Hello World App Explanation (Xcode 8.2.1 Swift 3.1)

showMessage method

  @IBAction func showMessage() {

        let alertController = UIAlertController(title: "Welcome to My First App",

                                                message: "Hello World", preferredStyle: UIAlertControllerStyle.alert)

        alertController.addAction(UIAlertAction(title: "OK", style:

            UIAlertActionStyle.default, handler: nil))

        present(alertController, animated: true, completion: nil)

    }

1. Func – keyword to declare a method

2. showMessage() – method name and parameters

3. @IBAction – keyword to expose the method to interface builder

4. import – keyword to access external frameworks ( ex. UIkit)

5. let – to define a constant

6. alertController – constant name

7. UIAlertController(title: "Welcome to My First App", message: "Hello World", preferredStyle: UIAlertControllerStyle.alert) – an object in which we specify the title, message and the style of the alert

8. alertController.addAction – it is a method to add action to the alert so that is displays “OK” button

9. present – present alertController object with animation