Swift Architecture: A Comprehensive Guide to MVC, MVVM & VIPER
The Swift programming language is a powerful tool for creating robust and responsive iOS applications. With the release of Swift 5, developers now have access to a range of different architectures that can be used to create high-performance apps. In this article, we’ll take a look at the three most popular architectures: Model-View-Controller (MVC), Model-View-ViewModel (MVVM), and View-Interactor-Presenter-Entity (VIPER). We’ll discuss the advantages and disadvantages of each architecture and provide code examples to help you understand how they work.
Model-View-Controller (MVC)
The Model-View-Controller (MVC) architecture is one of the oldest and most widely used architectures for iOS development. It divides the application into three components: the model, the view, and the controller. The model is responsible for the data and business logic of the application, while the view is responsible for displaying the data to the user. The controller acts as an intermediary between the model and the view, processing user input and updating the view accordingly.
Advantages
MVC is a simple architecture that is easy to understand and implement. It is also highly extensible, allowing developers to add additional features and functionality with relative ease.
Disadvantages
One of the major drawbacks of the MVC architecture is that it can become difficult to maintain as the application grows in size and complexity. As the number of controllers increases, it can become difficult to keep track of which view is being managed by which controller. Additionally, the tight coupling between the model and the view can make it difficult to reuse components across different projects.
Example
In the following example, we’ll use the MVC architecture to create a simple view controller that displays a list of items. First, we’ll create the model:
class Item {
var name: String
var price: Double
init(name: String, price: Double) {
self.name = name
self.price = price
}
}Next, we’ll create the view controller. This will be responsible for displaying the list of items to the user and handling user interactions.
class ItemListViewController: UIViewController {
var items: [Item] = []
override func viewDidLoad() {
super.viewDidLoad()
// Fetch items from the server
fetchItems()
}
func fetchItems() {
// Fetch items from the server
}
func displayItems() {
// Display items in the view
}
func handleItemSelection(item: Item) {
// Handle item selection
}
}Finally, we’ll create the controller. This will be responsible for managing the interactions between the model and the view.
class ItemListController {
var viewController: ItemListViewController
var items: [Item] = []
init(viewController: ItemListViewController) {
self.viewController = viewController
}
func fetchItems() {
// Fetch items from the server
items = // Fetch items from the server
viewController.items = items
viewController.displayItems()
}
func handleItemSelection(item: Item) {
// Handle item selection
viewController.handleItemSelection(item: item)
}
}As you can see, the controller is responsible for managing the interactions between the model and the view. The view controller is only responsible for displaying the data to the user, while the controller is responsible for managing the interactions between the two.
Model-View-ViewModel (MVVM)
The Model-View-ViewModel (MVVM) architecture is a variation of the MVC architecture. It divides the application into three components: the model, the view, and the view model. The model is responsible for the data and business logic of the application, while the view is responsible for displaying the data to the user. The view model acts as an intermediary between the model and the view, processing user input and updating the view accordingly.
Advantages
MVVM is a flexible architecture that allows developers to easily separate the view from the model. This makes it easier to test and maintain the code, as well as reuse components across different projects. Additionally, the view model is responsible for managing the interactions between the model and the view, which reduces the amount of code required in the view controller.
Disadvantages
One of the major drawbacks of the MVVM architecture is that it can be difficult to debug. Additionally, it can be difficult to ensure that the view and view model are always in sync, as changes in the view may not always be reflected in the view model.
Example
In the following example, we’ll use the MVVM architecture to create a simple view controller that displays a list of items. First, we’ll create the model:
class Item {
var name: String
var price: Double
init(name: String, price: Double) {
self.name = name
self.price = price
}
}Next, we’ll create the view controller. This will be responsible for displaying the list of items to the user and handling user interactions.
class ItemListViewController: UIViewController {
var viewModel: ItemListViewModel!
override func viewDidLoad() {
super.viewDidLoad()
viewModel.fetchItems()
}
func displayItems() {
// Display items in the view
}
func handleItemSelection(item: Item) {
// Handle item selection
}
}Finally, we’ll create the view model. This will be responsible for managing the interactions between the model and the view.
class ItemListViewModel {
var viewController: ItemListViewController
var items: [Item] = []
init(viewController: ItemListViewController) {
self.viewController = viewController
}
func fetchItems() {
// Fetch items from the server
items = // Fetch items from the server
viewController.displayItems()
}
func handleItemSelection(item: Item) {
// Handle item selection
viewController.handleItemSelection(item: item)
}
}As you can see, the view model is responsible for managing the interactions between the model and the view. The view controller is only responsible for displaying the data to the user, while the view model is responsible for managing the interactions between the two.
View-Interactor-Presenter-Entity (VIPER)
The View-Interactor-Presenter-Entity (VIPER) architecture is a more complex variation of the MVC and MVVM architectures. It divides the application into four components: the view, the interactor, the presenter, and the entity. The view is responsible for displaying the data to the user, while the interactor is responsible for handling user interactions. The presenter is responsible for processing user input and updating the view accordingly. Finally, the entity is responsible for managing the data and business logic of the application.
Advantages
VIPER is a highly modular architecture that makes it easy to reuse components across different projects. Additionally, the separation of concerns between components makes it easier to test and maintain the code.
Disadvantages
One of the major drawbacks of the VIPER architecture is that it can be difficult to understand and implement. Additionally, the number of components can make it difficult to keep track of which component is responsible for which task.
Example
In the following example, we’ll use the VIPER architecture to create a simple view controller that displays a list of items. First, we’ll create the entity:
class Item {
var name: String
var price: Double
init(name: String, price: Double) {
self.name = name
self.price = price
}
}Next, we’ll create the view controller. This will be responsible for displaying the list of items to the user and handling user interactions.
class ItemListViewController: UIViewController {
var presenter: ItemListPresenter!
override func viewDidLoad() {
super.viewDidLoad()
presenter.fetchItems()
}
func displayItems() {
// Display items in the view
}
func handleItemSelection(item: Item) {
// Handle item selection
}
}Then, we’ll create the interactor. This will be responsible for handling user interactions.
class ItemListInteractor {
var presenter: ItemListPresenter!
func fetchItems() {
// Fetch items from the server
let items = // Fetch items from the server
presenter.didFetchItems(items: items)
}
func handleItemSelection(item: Item) {
// Handle item selection
presenter.didSelectItem(item: item)
}
}Finally, we’ll create the presenter. This will be responsible for processing user input and updating the view accordingly.
class ItemListPresenter {
var viewController: ItemListViewController
var interactor: ItemListInteractor!
var items: [Item] = []
init(viewController: ItemListViewController) {
self.viewController = viewController
}
func fetchItems() {
interactor.fetchItems()
}
func didFetchItems(items: [Item]) {
self.items = items
viewController.displayItems()
}
func didSelectItem(item: Item) {
// Handle item selection
viewController.handleItemSelection(item: item)
}
}As you can see, the presenter is responsible for managing the interactions between the view and the interactor. The view controller is only responsible for displaying the data to the user, while the presenter is responsible for managing the interactions between the two.
In conclusion, the Swift programming language provides developers with a wide range of architectures to choose from. Each