Intro to iOS Development
  • Welcome
    • ☀️Introduction
    • 🐣Getting Started
    • 🐦Course Staff
  • Logistics
    • 📜Syllabus
    • 🗓️Schedule
    • 🖊️Grading
    • 🙋‍♂️Office Hours
    • Ed Discussion
  • Assignments
    • 🍼A1: Swift Basics
    • 🧑A2: Profile
    • 💬A3: ChatDev
    • 👨‍🍳A4: ChefOS
    • 👨‍🍳A4: ChefOS - SwiftUI
    • 📱Hack Challenge
      • 🏆FA23 Winners
  • Lectures
    • 1️⃣Logistics + Swift Basics
    • 2️⃣UIKit + AutoLayout
  • 3️⃣MVC + Navigation + Delegation
  • 4️⃣UITableView
  • 5️⃣UICollectionView
  • 6️⃣Networking I
  • 7️⃣Networking II
  • 8️⃣SwiftUI I
  • 9️⃣SwiftUI II
  • 🔟Persistence + SnapKit
  • 🔔(11) Notifications
  • 🌎(12) Deployment and MapKit
  • Chapters
    • 🖐️Introduction
    • ☁️Git + GitHub
      • 1️⃣Git Installation
      • 2️⃣Git Basics
      • ➕Git+
    • 🐣Swift Basics
      • 1️⃣Variables and Constants
      • 2️⃣Data Types
      • 3️⃣Operators
      • 4️⃣Data Structures
      • 5️⃣Conditionals
      • 6️⃣Loops
      • 7️⃣Functions
      • 8️⃣Closures
      • 9️⃣Optionals
    • 🧰UIKit + AutoLayout
      • 1️⃣Classes
      • 2️⃣UIKit
      • 3️⃣AutoLayout
    • 📺MVC + Navigation + Delegation
      • 1️⃣MVC
      • 2️⃣Navigation
      • 3️⃣Delegation
    • 🏓UITableView
      • 1️⃣What is a UITableView?
      • 2️⃣UITableView Setup
    • 📚UICollectionView
      • 1️⃣What is a UICollectionView?
      • 2️⃣UICollectionView Setup
    • 🌐Networking I
      • 1️⃣HTTP Requests
      • 2️⃣Callbacks
      • 3️⃣Codable
    • 🌍Networking II
      • 1️⃣Alamofire
      • 2️⃣GET Requests
      • 3️⃣POST Requests
      • 4️⃣URLSession
    • 💾Persistence + SnapKit
      • 1️⃣Persistence
      • 2️⃣SnapKit
    • 🕊️SwiftUI
      • 1️⃣Introduction to SwiftUI
      • 2️⃣Getting Started with SwiftUI
      • 3️⃣Views + Modifiers
      • 4️⃣Layouts
      • 5️⃣Navigation
      • 6️⃣Property Wrappers
    • 🎛️Widgets
      • 1️⃣Introduction to Widgets
      • 2️⃣Setting Up Widgets
      • 3️⃣Building Widgets
      • 4️⃣Configuring Widgets
    • 🧱Project Foundation
    • ✅Testing
      • 1️⃣Unit Testing
    • 👣Debugging
      • 1️⃣OSLog
      • 2️⃣Crashlytics
      • 3️⃣Analytics
    • ☁️CI/CD
      • 1️⃣Xcode Cloud
      • 2️⃣AppStore Shipping
  • Guides
    • 🔨Xcode Project Setup
    • 🎨Figma
    • 📬Postman
    • 🥥CocoaPods
    • 🧰UIKit Handbook
    • 📑Tab Views
      • UITabBarController
      • TabView
  • Work in progress
    • 🧵Concurrency
    • 2️⃣UI Testing
    • 🕐Reactive Programming
    • 🧠Memory Management
      • 🔁ARC
    • 📦Storage
    • 📣Notifications
  • Archived
    • SP24
      • Logistics
        • 📜Syllabus
        • 🗓️Schedule
        • 🖊️Grading
        • 🙋‍♂️Office Hours
      • Assignments
        • 🍼A1: Swift Basics
        • 🧑A2: Profile
        • 💬A3: ChatDev
        • 👨‍🍳A4: ChefOS
        • 📱Hack Challenge
          • 🏆FA23 Winners
      • Lecture
        • 0️⃣Course Intro + Logistics + Git Setup
        • 1️⃣Swift Basics
        • 2️⃣UIKit + AutoLayout
        • 3️⃣MVC + Navigation + Delegation
        • 4️⃣UITableView
        • 5️⃣UICollectionView
        • 6️⃣Networking I
        • 7️⃣Networking II
        • 8️⃣Persistence + SnapKit
        • 🔟SwiftUI
        • 🔢TabViews
    • FA23
      • Logistics
        • 🐣Getting Started
        • 🐦Course Staff
        • 📜Syllabus
        • 🗓️Schedule
        • 🖊️Grading
        • 🙋‍♂️Office Hours
      • Assignments
        • 🍼A1: Swift Basics
        • 🧑A2: Profile
        • 💬A3: ChatDev
        • 👨‍🍳A4: ChefOS
        • 📱Hack Challenge
          • 🏆FA23 Winners
      • Lectures
        • 0️⃣Course Intro + Logistics
        • 1️⃣Swift Basics
        • 2️⃣UIKit + AutoLayout
        • 3️⃣MVC + Navigation + Delegation
        • 4️⃣UITableView
        • 5️⃣UICollectionView
        • 6️⃣Networking I
        • 7️⃣Networking II
        • 8️⃣Persistence + SnapKit
        • 🎛️Widgets
          • 👼Introduction to Widgets
          • ⚒️Setting Up Widgets
          • 🧱Building Widgets
          • 👨‍💻Configuring Widgets
        • 🔟SwiftUI
    • SP23
      • Logistics
        • Lecture Schedule
        • Syllabus
        • Grading
        • SP23 Office Hours
      • Chapters
        • 1. Intro to Swift & Xcode
          • Lecture Handout
          • Lecture Demo
          • 🍼Project: Swift Basics
        • 2. UIKit and AutoLayout
          • Lecture Handout
          • Lecture Demo
          • 🛒Project: UIKit + AutoLayout
        • 3. Navigation, MVC, and Delegation
          • Lecture Handout
          • Lecture Demo
          • Project: Navigation + Delegation
        • 4. UITableView
          • Lecture Handout
          • Lecture Demo
          • Project: UITableView
        • 5. UICollectionView
          • Lecture Handout
          • Lecture Demo
          • Project: UICollectionView
        • 6. Networking I
          • Lecture Handout
          • Lecture Demo
          • Project: Persistence
        • 7. Networking II
          • Lecture Handout
          • Lecture Demo
            • Message Board
          • Project: Networking II
        • 8. Swift UI
        • 9. CocoaPods
          • 🍫Lecture Handout
          • 🧑‍🍳Lecture Demo
      • Cheat Sheets
        • Setting Up a New Xcode Project
        • Submitting Your Projects
        • Setting Up CocoaPods
    • 2022
      • SwiftUI
    • 2021
      • Adding Flare
      • Project: UIView Animations (Optional - Extra Credit)
      • UIView Animations
      • Xcode Tips and Tricks
    • 2019
      • Firebase
      • Persistence: UserDefaults
  • Swift Guide (ARCHIVED)
    • About this Textbook
    • Documentation
    • Constants and Variables
      • Variable Properties
      • Lazy and Static Variables
    • Functions
    • Ranges
    • Arrays
      • Basic Array Operations
      • Iteration and Enumeration
      • Advanced Array Operations
    • Tuples
    • Conditions and While Loops
    • For Loops
    • Enums and Switches
      • Enums with Associated Values
      • Indirect Enums
    • Classes and Structs
    • Optionals
    • Dictionaries
      • Dictionary Implementation
    • Closures
    • Constraints
    • Generics
    • Protocols
      • Protocols With Associated Types
    • Casting
    • Errors
    • Networking
      • Result
    • Inout
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  • Model
  • View
  • Controller
  • Putting everything together

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  1. Chapters
  2. MVC + Navigation + Delegation

MVC

Fall 2023 | Vin Bui

In the previous chapter, we learned what views are and how to create views in UIKit. We also learned how to use AutoLayout to position our views on the screen. However, our views contained hard coded data and did not have any functionality at all. When we create apps, we want our views to respond and update to user interactions.

MVC (Model-View-Controller) is a software design pattern which is a set of rules that govern the architecture that we follow when writing our code. There are other design patterns out there such as MVVM (Model-View-ViewModel) but we will be using MVC throughout this course. To better understand MVC, let’s take a deeper look at each component.

Model

Models are objects that represent our application’s data. Let’s look at an app we are familiar with, Eatery. The models in Eatery are the dining halls, the dishes and food items, the user’s information, etc. In other words, models contain information about our application and are often updated based on user interaction or from a backend service.

Classes vs Structs

Notice that we often use structs instead of classes when representing our models. The difference between these two is that structs are value types whereas classes are reference types. What this means is that if we were to change a property of an instance of a struct, the entire instance changes. On the other hand, if we change a property of an instance of a class, the instance does not change.

For example, consider a User model with the property name. For a class object (reference type), if we changed the value of name, all locations that have a reference to that object have the new updated value for name. If this were to be a struct object (value type), changing the value of name in one location DOES NOT update other locations because a new instance is being created. We can think of reference types as sharing a Google Doc with other collaborators. If one person were to change something on their side, the others would be able to see those changes. For structs, we can think of it as making a copy of the Google Doc.

One advantage of using a class is inheritance. In other words, we can use properties and methods already defined by a parent class, commonly seen in UIKit. However, there are times when we don't need to use all of these properties and methods, making structs more preferable. This is commonly seen in SwiftUI and why using structs is a lot faster than classes.

View

Views are the visible components that are used to build the user interface (UI). This includes buttons, labels, images, etc. In Eatery, everything we see is a view. For example, the name of the dining hall is a UILabel which contains information from the dining hall model. We don’t see models. We see views that contain information from the models.

Controller

Controllers belong in the middle between models and views. The main goal of a controller is to establish a connection between models and views. The controller is also in charge of processing the logic to update the models and views. For example, in Eatery, there is a User model that represents the logged in user. When we sign in, we are interacting with views. How does the model update based on what we passed into the text field? Well the controller handles that logic. If we provided the correct credentials, it will modify the models and update the views such as showing a logout button. If we provided invalid credentials, then the controller will still update the view and show a red error message.

Putting everything together

One important thing to keep note of is that views and models are separate. They cannot directly interact with each other, but rather, they must go through a controller to make that connection.

We can think of MVC as watching television: the TV is the view, the remote is the controller, and the channels/content is the model. How does the TV (view) change the channel (model)? It can’t! We must use a remote (controller) in order to do that. When we change channels using the remote, we made changes to the model and tell the TV to update its view.

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