MVC stands for Model-View-Controller, and it's a widespread architectural pattern for software development. It's the de facto design pattern for Cocoa development, and it has been for many, many years. Most of us can't imagine building applications without it. Both UIKit (iOS) and AppKit (macOS) make frequent use of MVC. It almost seems as if we don't have another option to build applications for iOS, tvOS, macOS, and watchOS.
Let me show you what the MVC pattern looks like in a typical Cocoa application. The example I'll be showing you focuses on iOS, but everything we discuss also applies to tvOS, macOS, and watchOS. Open Xcode and create a new iOS project based on the Single View Application template.
Name the project MVC, and set Language to Swift and Devices to iPhone. I'm using Xcode 8 for this tutorial. The project's configuration options may look a bit different if you're using Xcode 9.
The controllers of an iOS application are view controllers, instances of the UIViewController class or a subclass thereof. The UIViewController class is defined in the UIKit framework. Because we chose the Single View Application template when we set up the project, Xcode created a controller for us to start with, the ViewController class, defined in ViewController.Swift. It inherits from the UIViewController class.