Getting began with VIPER
To start with, it’s best to learn my earlier (extra theoretical) article in regards to the VIPER structure itself. It is a fairly first rate writing explaining all of the VIPER elements and reminiscence administration. I’ve additionally polished it a bit bit, final week. ⭐️
The issue with that article nevertheless was that I have not present you the actual deal, aka. the Swift code for implementing VIPER. Now after a full yr of initiatives utilizing this structure I can lastly share all my finest practices with you.
So, let’s begin by making a model new Xcode undertaking, use the one view app template, identify the undertaking (VIPER finest practices), use Swift and now you are able to take the following step of constructing an superior “enterprise grade” iOS app.
Producing VIPER modules
Lesson 1: by no means create a module by hand, all the time use a code generator, as a result of it is a repetative activity, it is fuckin’ boring plus it’s best to give attention to extra essential issues than making boilerplate code. You should utilize my light-weight module generator known as:
This part is outdated, it’s best to use the swift template repository.
Simply obtain or clone the repository from GitHub. You may set up the binary software by operating swift run set up –with-templates. This may set up the vipera app underneath /usr/native/bin/ and the fundamental templates underneath the ~/.vipera listing. You should utilize your personal templates too, however for now I will work with the default one. 🔨
I normally begin with a module known as Important that is the basis view of the appliance. You may generate it by calling vipera Important within the undertaking listing, so the generator can use the right undertaking identify for the header feedback contained in the template recordsdata.
Clear up the undertaking construction a bit bit, by making use of my conventions for Xcode, which means that sources goes to an Belongings folder, and all of the Swift recordsdata into the Sources listing. These days I additionally change the AppDelegate.swift file, and I make a separate extension for the UIApplicationDelegate protocol.
Create a Modules group (with a bodily folder too) underneath the Sources listing and transfer the newly generated Important module underneath that group. Now repair the undertaking points, by choosing the Information.plist file from the Belongings folder for the present goal. Additionally do take away the Important Interface, and after that you could safely delete the Important.storyboard and the ViewController.swift recordsdata, as a result of we’re not going to wish them in any respect.
Contained in the AppDelegate.swift file, you must set the Important module’s view controller as the basis view controller, so it ought to look considerably like this:
import UIKit
@UIApplicationMain
class AppDelegate: UIResponder {
var window: UIWindow?
}
extension AppDelegate: UIApplicationDelegate {
func software(_ software: UIApplication,
didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
self.window = UIWindow(body: UIScreen.foremost.bounds)
self.window?.rootViewController = MainModule().buildDefault()
self.window?.makeKeyAndVisible()
return true
}
}Congratulations, you’ve got created your very first VIPER module! 🎉
UITabBarController & VIPER
I’ve a brilliant easy answer for utilizing a tab bar controller in a VIPER module. First let’s generate a couple of new modules, these are going to be the tabs. I’ll use the JSONPlaceholder service, so lets say a separate tab for every of those sources: posts, albums, images, todos (with the identical module identify). Generate all of them, and transfer them into the modules folder.
Now, let’s generate yet another module known as House. This may implement our tab bar controller view. If you need you need to use the Important module for this goal, however I wish to preserve that for animation functions, to have a neat transition between the loading display and my House module (all of it will depend on your wants).
So the principle logic that we’ll implement is that this: the principle view will notify the presenter in regards to the viewDidAppear occasion, and the presenter will ask the router to show the House module. The House module’s view can be a subclass of a UITabBarController, it’s going to additionally notify it is presenter about viewDidLoad, and the presenter will ask for the right tabs, by utilizing its router.
Right here is the code, with out the interfaces:
class MainDefaultView: UIViewController {
var presenter: MainPresenter?
override func viewDidAppear(_ animated: Bool) {
tremendous.viewDidAppear(animated)
self.presenter?.viewDidAppear()
}
}
extension MainDefaultPresenter: MainPresenter {
func viewDidAppear() {
self.router?.showHome()
}
}
extension MainDefaultRouter: MainRouter {
func showHome() {
let viewController = HomeModule().buildDefault()
self.viewController?.current(viewController, animated: true, completion: nil)
}
}
extension HomeDefaultView: HomeView {
func show(_ viewControllers: [UIViewController]) {
self.viewControllers = viewControllers
}
}
extension HomeDefaultPresenter: HomePresenter {
func setupViewControllers() {
guard let controllers = self.router?.getViewControllers() else {
return
}
self.view?.show(controllers)
}
}
extension HomeDefaultRouter: HomeRouter {
func getViewControllers() -> [UIViewController] {
return [
PostsModule().buildDefault(),
AlbumsModule().buildDefault(),
PhotosModule().buildDefault(),
TodosModule().buildDefault(),
].map { UINavigationController(rootViewController: $0) }
}
}
class HomeModule {
func buildDefault() -> UIViewController {
presenter.setupViewControllers()
return view
}
}There may be one further line contained in the House module builder perform that triggers the presenter to setup correct view controllers. That is simply because the UITabBarController viewDidLoad technique will get known as earlier than the init course of finishes. This behaviour is sort of undocumented however I assume it is an UIKit hack in an effort to preserve the view references (or only a easy bug… is anybody from Apple right here?). 😊
Anyway, now you might have a correct tab bar contained in the undertaking built-in as a VIPER module. It is time to get some information from the server and right here comes one other essential lesson: not every little thing is a VIPER module.
Providers and entities As you would possibly seen there isn’t any such factor as an Entity inside my modules. I normally wrap APIs, CoreData and lots of extra information suppliers as a service. This manner, all of the associated entities will be abstracted away, so the service will be simply changed (with a mock for instance) and all my interactors can use the service by way of the protocol definition with out realizing the underlying implementation.
One other factor is that I all the time use my promise library if I’ve to cope with async code. The explanation behind it’s fairly easy: it is far more elegant than utilizing callbacks and elective consequence parts. You need to be taught guarantees too. So right here is a few a part of my service implementation across the JSONPlaceholder API:
protocol Api {
func posts() -> Promise<[Post]>
func feedback(for put up: Put up) -> Promise<[Comment]>
func albums() -> Promise<[Album]>
func images(for album: Album) -> Promise<[Photo]>
func todos() -> Promise<[Todo]>
}
struct Put up: Codable {
let id: Int
let title: String
let physique: String
}
class JSONPlaceholderService {
var baseUrl = URL(string: "https://jsonplaceholder.typicode.com/")!
enum Error: LocalizedError {
case invalidStatusCode
case emptyData
}
personal func request<T>(path: String) -> Promise<T> the place T: Decodable {
let promise = Promise<T>()
let url = baseUrl.appendingPathComponent(path)
print(url)
URLSession.shared.dataTask(with: url) { information, response, error in
if let error = error {
promise.reject(error)
return
}
guard let httpResponse = response as? HTTPURLResponse, httpResponse.statusCode == 200 else {
promise.reject(Error.invalidStatusCode)
return
}
guard let information = information else {
promise.reject(Error.emptyData)
return
}
do {
let mannequin = strive JSONDecoder().decode(T.self, from: information)
promise.fulfill(mannequin)
}
catch {
promise.reject(error)
}
}.resume()
return promise
}
}
extension JSONPlaceholderService: Api {
func posts() -> Promise<[Post]> {
return self.request(path: "posts")
}
}Often I’ve a mock service implementation subsequent to this one, so I can simply check out every little thing I would like. How do I swap between these companies? Nicely, there’s a shared (singleton – do not hate me it is fully tremendous 🤪) App class that I take advantage of largely for styling functions, however I additionally put the dependency injection (DI) associated code there too. This manner I can go round correct service objects for the VIPER modules.
class App {
static let shared = App()
personal init() {
}
var apiService: Api {
return JSONPlaceholderService()
}
}
class PostsModule {
func buildDefault() -> UIViewController {
let view = PostsDefaultView()
let interactor = PostsDefaultInteractor(apiService: App.shared.apiService)
return view
}
}
class PostsDefaultInteractor {
weak var presenter: PostsPresenter?
var apiService: Api
init(apiService: Api) {
self.apiService = apiService
}
}
extension PostsDefaultInteractor: PostsInteractor {
func posts() -> Promise<[Post]> {
return self.apiService.posts()
}
}You are able to do this in a 100 different methods, however I presently desire this method. This manner interactors can instantly name the service with some additional particulars, like filters, order, type, and so forth. Principally the service is only a excessive idea wrapper across the endpoint, and the interactor is creating the fine-tuned (higher) API for the presenter.
Making guarantees
Implementing the enterprise logic is the duty of the presenter. I all the time use guarantees so a fundamental presenter implementation that solely masses some content material asynchronously and shows the outcomes or the error (plus a loading indicator) is just some traces lengthy. I am all the time attempting to implement the three fundamental UI stack parts (loading, information, error) by utilizing the identical protocol naming conventions on the view. 😉
On the view facet I am utilizing my good outdated assortment view logic, which considerably reduces the quantity of code I’ve to jot down. You may go together with the standard method, implementing a couple of information supply & delegate technique for a desk or assortment view is just not a lot code in any case. Right here is my view instance:
extension PostsDefaultPresenter: PostsPresenter {
func viewDidLoad() {
self.view?.displayLoading()
self.interactor?.posts()
.onSuccess(queue: .foremost) { posts in
self.view?.show(posts)
}
.onFailure(queue: .foremost) { error in
self.view?.show(error)
}
}
}
class PostsDefaultView: CollectionViewController {
var presenter: PostsPresenter?
init() {
tremendous.init(nibName: nil, bundle: nil)
self.title = "Posts"
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been applied")
}
override func viewDidLoad() {
tremendous.viewDidLoad()
self.presenter?.viewDidLoad()
}
}
extension PostsDefaultView: PostsView {
func displayLoading() {
print("loading...")
}
func show(_ posts: [Post]) {
let grid = Grid(columns: 1, margin: UIEdgeInsets(all: 8))
self.supply = CollectionViewSource(grid: grid, sections: [
CollectionViewSection(items: posts.map { PostViewModel($0) })
])
self.collectionView.reloadData()
}
func show(_ error: Error) {
print(error.localizedDescription)
}
}The cell and the ViewModel is exterior the VIPER module, I are likely to dedicate an App folder for the customized software particular views, extensions, view fashions, and so forth.
class PostCell: CollectionViewCell {
@IBOutlet weak var textLabel: UILabel!
}
class PostViewModel: CollectionViewViewModel<PostCell, Put up> {
override func config(cell: PostCell, information: Put up, indexPath: IndexPath, grid: Grid) {
cell.textLabel.textual content = information.title
}
override func measurement(information: Put up, indexPath: IndexPath, grid: Grid, view: UIView) -> CGSize {
let width = grid.width(for: view, objects: grid.columns)
return CGSize(width: width, peak: 64)
}
}Nothing particular, if you would like to know extra about this assortment view structure, it’s best to learn my different tutorial about mastering assortment views.
Module communication
One other essential lesson is to discover ways to talk between two VIPER modules. Usually I’m going with easy variables – and delegates if I’ve to ship again some type of data to the unique module – that I go round contained in the construct strategies. I’ll present you a extremely easy instance for this too.
class PostsDefaultRouter {
weak var presenter: PostsPresenter?
weak var viewController: UIViewController?
}
extension PostsDefaultRouter: PostsRouter {
func showComments(for put up: Put up) {
let viewController = PostDetailsModule().buildDefault(with: put up, delegate: self)
self.viewController?.present(viewController, sender: nil)
}
}
extension PostsDefaultRouter: PostDetailsModuleDelegate {
func toggleBookmark(for put up: Put up) {
self.presenter?.toggleBookmark(for: put up)
}
}
protocol PostDetailsModuleDelegate: class {
func toggleBookmark(for put up: Put up)
}
class PostDetailsModule {
func buildDefault(with put up: Put up, delegate: PostDetailsModuleDelegate? = nil) -> UIViewController {
let view = PostDetailsDefaultView()
let interactor = PostDetailsDefaultInteractor(apiService: App.shared.apiService,
bookmarkService: App.shared.bookmarkService)
let presenter = PostDetailsDefaultPresenter(put up: put up)
return view
}
}
class PostDetailsDefaultRouter {
weak var presenter: PostDetailsPresenter?
weak var viewController: UIViewController?
weak var delegate: PostDetailsModuleDelegate?
}
extension PostDetailsDefaultRouter: PostDetailsRouter {
func toggleBookmark(for put up: Put up) {
self.delegate?.toggleBookmark(for: put up)
}
}
class PostDetailsDefaultPresenter {
var router: PostDetailsRouter?
var interactor: PostDetailsInteractor?
weak var view: PostDetailsView?
let put up: Put up
init(put up: Put up) {
self.put up = put up
}
}
extension PostDetailsDefaultPresenter: PostDetailsPresenter {
func reload() {
self.view?.setup(with: self.interactor!.bookmark(for: self.put up))
self.interactor?.feedback(for: self.put up)
.onSuccess(queue: .foremost) { feedback in
self.view?.show(feedback)
}
.onFailure(queue: .foremost) { error in
}
}
func toggleBookmark() {
self.router?.toggleBookmark(for: self.put up)
self.view?.setup(with: self.interactor!.bookmark(for: self.put up))
}
}Within the builder technique I can entry each part of the VIPER module so I can merely go across the variable to the designated place (identical applies for the delegate parameter). I normally set enter variables on the presenter and delegates on the router.
It is normally a presenter who wants information from the unique module, and I wish to retailer the delegate on the router, as a result of if the navigation sample modifications I haven’t got to vary the presenter in any respect. That is only a private choice, however I like the best way it appears like in code. It is actually onerous to jot down down these items in a single article, so I might suggest to obtain my completed pattern code from GitHub.
Abstract
As you possibly can see I am utilizing varied design patterns on this VIPER structure tutorial. Some say that there isn’t any silver bullet, however I imagine that I’ve discovered a extremely superb methodology that I can activate my benefit to construct high quality apps in a short while.
Combining Guarantees, MVVM with assortment views on high of a VIPER construction merely places each single piece into the precise place. Over-engineered? Perhaps. For me it is definitely worth the overhead. What do you concentrate on it? Be happy to message me by way of twitter. It’s also possible to subscribe to my month-to-month publication under.