MVC, Model Objects, Model Object Controllers

Objectives

Model-View-Controller is an essential design pattern to follow when developing for iOS. We will talk about following MVC principles as we architect and plan our our applications.

This lesson provides many examples for thinking through MVC architecture in a variety of contexts. Students should not get hung up on all of the different examples, but should focus on the MVC concepts.

• You will be able to describe, identify, and implement proper Model-View-Controller principles
• You will be able to create a custom class for storing model data
• You will be able to store data on and retrieve data from a model controller object
• You will be able to identify, describe, and implement the singleton pattern

Required Preclass Resources

• Stanford iOS Development MVC Description

  Watch from 13:30 - 29:55.

• Apple's MVC Documentation
• Understanding Model-View-Controller
• Cocoa Core Competencies: Model Objects
• Cocoa Core Competencies - Controller Objects
• Create, Read, Update, and Delete
• Cocoa Core Competencies - Singleton
• Avoiding Singleton Abuse
• Singletons, AppDelegates, and Top-Level Data

Lesson Video

Video Challenges

• Plan MVC Architecture for a Family Recipes App

  Draw the MVC triangle. Take 5 minutes to think through a simple Family Recipe App listing favorite family recipes. What type of model objects are there? What types of views are there? What View Controllers are there? What model controllers would be helpful? Add each of them to a list. Discuss with your neighbor.

• Cars

  Create a Playground and define a Car class with properties for make, model, year, vin. Create a memberwise initializer. Initialize three different objects.

• Bookshelf

  Do the following in a new Playground.

  • Create a Book object with title, author, and genre properties, and a memberwise initializer.
  • Create a Bookshelf object that will serve as a model object controller. The Bookshelf should have a books array and addBook(book: Book) and removeBook(book: Book) functions that manage the array.
  • Create a couple of books and add/remove them from the array in the Playground.
• Create Your Own Singleton

  Give the students 5-10 minutes to build a model and controller for an application for a Parking Structure.

  Car.swift -> make, model, year, etc CarController.swift -> sharedController, parkedCars, addCar, removeCar

  We are not doing any persistence yet. They should have a simple model object and a controller that holds an array of the objects.

Stretch Problem

Equatable

Start with the following code:

class Person {
  let firstName: String
  let lastName: String
  let age: Int

  init(firstName: String, lastName: String, age: Int) {
    self.firstName = firstName
    self.lastName = lastName
    self.age = age
  }
}

let james = Person(firstName: "James", lastName: "Pacheco", age: 26)
let andrea = Person(firstName: "Andrea", lastName: "Mower", age: 24)
let carol = Person(firstName: "Rebecca", lastName: "Mordo", age: 30)

let clubMembers: [Person] = [james, andrea, carol]

1. Initialize two more Person objects. Add one of them to the club array, but do not add the other.
2. Now, create a function called areYouAMemberOfTheClub that takes a Person object as a parameter and returns a Bool indicating whether or not the person passed in is a member of the club. It should return true for the person that you added to the array of club members and false for the other person.
   • note: there are a couple of ways to do this, but in all ways you will be using the clubMembers array as a reference.
3. Perhaps you thought the best way to accomplish the above task was to loop through the clubMembers array in your function and see if the person passed in is equal to any of them using person == clubMembers[i], or something along those lines. Notice that you cannot use the == operator. This is because you must conform to the Equatable protocol. Go look it up in documentation.
4. Make the Person object conform to the Equatable protocol and outside of the Person class create the necessary Equatable function. You should now be able to use the == operator between two Person objects, making it easier to make your areYouAMemberOfTheClub function. By conforming to the Equatable protocol, you are also given some array methods that help solve this problem (you don't have to use them, but they make your life easier).

♦ Black Diamond

Create a new X-Code Project called ClubMembers. Copy over your Person class, clubMembers array, and make a new array that contains all of your Person objects, whether club members or not. Make sure to copy over your Equatable function as well (all of these should be put into the proper files, which you'll need to make). Then create a tableView that displays all people with a subtitle that says club member or not a club member. Add a button that will reload your tableView and only show club members.

Hint

Solution

Guided Project

Playlist

Playlist teaches proper MVC design through creating Playlist and Song objects with corresponding controllers, and teaches the singleton pattern.

Project

• Journal

  Students will build a simple Journal app to practice MVC separation, protocols, master-detail interfaces, table views, and persistence.

  Journal is an excellent app to practice basic Cocoa Touch princples and design patterns. Students are encouraged to repeat building Journal regularly until the principles and patterns are internalized and the student can build Journal without a guide.

  ReadMe

Mastery Review