/swift-airportsAndEnums-lab-ios-0616

Primary LanguageSwiftOtherNOASSERTION

Airports & Enums

Airplane Landing

Objectives

  • Declare and define an enum to manage airport statuses

Introduction

You can instantly get the status of just about anything and airports are no different. This lab takes you on the wild ride of beautifully displaying airport status information. So have a seat because there will probably be delays.

Open your .xcworkspace file and take a look at the project navigator. The ViewController.swift file is where you will be doing all your work. Outlet properties are already hooked up, along with some enum properties.

There is an optional instance property on the class called airportDictionary of type NSDictionary. When viewDidLoad() is called airportDictionary gets its value by calling a class method defined in the Airport Status class. This method returns a dictionary containing statuses for five major US airports. Each status includes the airport's current delay information and weather. Click on the AirportStatus.swift file to take a peek and see all the instance properties. Even though it's not hooked up in this lab, the class is set up to work with information received from the FAA's REST API.

Head back to the ViewController.swift file. The file uses extensions to organize the different parts of the class. Scroll down to the // MARK: Enums line to view the extension of enums that are already defined for you including one that is not, // Airport Code Enum. This is the enum you will make. Let's get started.

1. Define the Airport Code enum

  • Declare an enum called AirportCode of type String.
  • Define cases for the following airport codes: ATL, DFW, JFK, LAX, ORD (keep them in alphabetical order).
    Hint: Is there a way to define the cases in one line?

2. Declare an AirportCode property on the class

Scroll up to the top of the ViewController.swift file to view all the instance properties. As mentioned before you will see some enum properties already declared.

  • Declare an optional enum property below the existing enum properties called airportCode of type AirportCode and assign a value of .ATL (That's one of your enum cases).
  • Scroll down to viewDidLoad() and add a print statement inside the function to print your airportCode property.
  • Build and run ⌘ + R the application. You should see the optional ending in ".ATL" printed out in the console.

3. Assign a raw value to airportCode from a key inside airportDictionary

Scroll to the airportDictionary instance property. You'll notice that the didSet property observer is defined for you. The code inside the observer unwraps the dictionary, sorts the keys, and grabs the first key value. The keys inside the dictionary are the same names as the AirportCode cases you defined in your enum. You're going to use the code constant to initialize your airportCode property.

  • Scroll up to your airportCode property and remove .ATL as the initial value. We will no longer assign an initial value here.
  • Back inside the didSet observer of airportDictionary, assign the initial value to airportCode using the raw value initializer. The initializer takes a string argument. Hint: Check out Apple's documentation and scroll down to the "Initializing from a Raw Value" section.
if let code = sortedKeys.first {

   // declare and assign the property

}
  • Build and run ⌘ + R the application. You should still see the optional ending in ".ATL" printed out in the console.

4. Add a didSet property observer to the airportCode property and assign a value to airportStatus

So far you have created an enum but it's not really doing much. airportDictionary contains all the airport statuses of type AirportStatus. Each AirportStatus object has all the information you need to assign values to your view properties but we need to get it out of the dictionary first. Now that airportCode has an initial value we can use its raw value to access a status in airportDictionary. Remember that the keys inside the dictionary match the case names of your enum ["ATL": <AirportStatus>].

  • Expand the declaration of the airportCode property to include a didSet property observer. Use the other properties in the class as a reference.
  • Inside the didSet property observer, assign a value to the airportStatus property. You can get the value by accessing airportDictionary. Use the raw value of airportCode as the key.
    Hint: Enums come with a .rawValue property.
    Hint: You will need to downcast to AirportStatus when accessing the status from the dictionary.
  • Build and run ⌘ + R the application. You should see a big control tower, a pretty moon, and a Delta airplane.

5. Add a mutating function to the AirportCode enum

The view has a gesture set up so the user can swipe left to load the next airport status. Build and run ⌘ + R the application. Swipe left a few times. While the transition might be fun, the information remains the same. You are going to change that! Scroll to your AirportCode enum to add a new method.

  • Add a mutating method called next() below your cases. Hint: Check out Apple's documentation and scroll to the section "Modifying Value Types from Within Instance Methods".
  • Inside the mutating method add a switch statement that switches self. The goal is to mutate the current value of self and change it to the next value (e.g., change ATL to DFW, DFW to JFK). The switch should be successive and exhaustive meaning the last case should switch self back to ATL.
  • Scroll to the section label // MARK: Gesture. Find the changeStatusWithAnimation() method. Use your airportCode property to call the next() method you just defined.
if statusReceived {

    // call next method here

    UIView.transitionWithView(view, duration: 0.5, options: .TransitionFlipFromRight, animations: nil, completion: nil)

}

When next() is called, the next airport status is retrieved from the airportDictionary and the view elements are updated with new information.

  • Build and run ⌘ + R the application. Start swiping left to see the status for each airport.
  • Test ⌘ + R the application.