CocoaHeads SKG #8 - Application Architecture

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1. iOS Application Architecture Part One CocoaheadsSKG Dimitri James Tsiflitzis
2. Intro Application architecture guides application design. Application architecture paradigms provide principles that influence design decisions and patterns that provide design solutions. It aims to make apps scalable, reliable, testable and manageable
3. Light View Controllers
4. Apple MVC Model App Data Controller Updates Model Controls View View User Presentation Human / Non-human
5. Table Views and Collection Views UITableViewController Dedicated view controller for table views Eliminate a lot of the boilerplate code that arises by using a tableview in a view controller UITableView displayed full screen so you are restricted in your layout options
6. override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCellWithIdentifier("ItemCell", forIndexPath: indexPath) as! ItemCell let item = items[indexPath.row] as! Item cell.nameLabel.text = myItem.name return cell } You may have come across this often time Handle Cell Configuration internally
7. Handle Cell Configuration internally Bring all of these assignments you see above into the table view cell subclass class ItemCell: UITableViewCell { func configure(item: Item) { self.nameLabel.text = item.name } }
8. Handle Cell Configuration internally override func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCellWithIdentifier("ItemCell", forIndexPath: indexPath) as! ItemCell cell.configure(items[indexPath.row] as! Item) return cell } And then we have simplified the data source right away
9. Use a Data Source Class class ItemDataSource: NSObject, UITableViewDataSource { let items = [Item(name:"1"), Item(name:"2"), Item(name:"3"), Item(name:"4")] // MARK: - DATA SOURCE func numberOfSectionsInTableView(tableView: UITableView) -> Int { return 1 } func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return items.count } func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCellWithIdentifier("ItemCell", forIndexPath: indexPath) as! ItemCell cell.configure(items[indexPath.row] as! Item) return cell } }
10. Use a Data Source Class class ItemListViewController: UITableViewController { let dataSource = ItemDataSource() // MARK: - LIFECYCLE override func viewDidLoad() { super.viewDidLoad() tableView.dataSource = dataSource } } Just assign your data source
11. Use a Data Source Class class ItemStore { private let items = [Item(name:"1"), Item(name:"2"), Item(name:"3"), Item(name:"4")] func allItems() -> [String] { return items } } Use a separate class for you items too
12. Use a Data Source Class class ItemDataSource: NSObject, UITableViewDataSource { let items = ItemStore() // MARK: - DATA SOURCE func numberOfSectionsInTableView(tableView: UITableView) -> Int { return 1 } func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int { return items.allItems() } func tableView(tableView: UITableView, cellForRowAtIndexPath indexPath: NSIndexPath) -> UITableViewCell { let cell = tableView.dequeueReusableCellWithIdentifier("ItemCell", forIndexPath: indexPath) as! ItemCell cell.configure(items.allItems()[indexPath.row]) return cell } } Your final product
13. Container & Child View Controllers Adding a container view controller in Interface Builder View Controller Container
14. Container View Controllers /* add */ let viewController = self.storyBoard.instantiateViewControllerWithIdentifier("test") self.addChildViewController(viewController) self.view.addSubview(viewController.view) viewController.didMoveToParentViewController(self) /* remove */ let controller = self.childViewControllers.lastObject() controller.view.removeFromSuperview() controller.removeFromParentViewController() In code
15. Communication
16. Delegation The delegating object holds a reference to the delegate object and at the appropriate time sends a messages or calls a method on it Delegate Container Table View height for row
17. Interlude: Objective-C Categories, Extensions and Swift extensions. Airport Airport.m Airport+Runway.m
18. Interlude: Objective-C Categories, Extensions and Swift extensions. extension SomeClass { /* add new functionality here */ }
19. Notification Centre NSNotificationCenter.defaultCenter().postNotificationName("notificationReceived", object: nil) This is how you post an NSNotification.
20. Notification Centre NSNotificationCenter.defaultCenter().addObserver(self, selector:#selector(notificationReceived(_:)), name: notificationReceived, object: nil) This is how you observe an NSNotification
21. Notification Centre func receiveNotification(notification : NSnotification) { } And of course, you’ll need to define the method that will be executed.
22. Key Value Observing (KVO) Key value observing is a mechanism that allows objects, as specific instances, to be notified of changes on properties of other object Second Object Container First Object notifies Property A
23. Key Value Observing (KVO) private var globalContext = 0 class Participant: NSObject { dynamic var name = "Maria" } class Observer: NSObject { var participant = Participant() override init() { super.init() participant.addObserver(self, forKeyPath: "name", options: .New, context: &globalContext) } override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) { if context == &globalContext { if let newValue = change?[NSKeyValueChangeNewKey] { print("Date changed: \(newValue)") } } else { super.observeValueForKeyPath(keyPath, ofObject: object, change: change, context: context) } } deinit { participant.removeObserver(self, forKeyPath: "name", context: &globalContext) } }
24. When to use the Notification Centre, Delegation or Key Value Observing Receiver Knows Sender Many Recipients Notification Notification Two Way Delegate Yes No No Yes KVO Notification Yes No
25. Patterns
26. Patterns /* definition */ class SwiftSingleton { static let sharedInstance = SwiftSingleton() private init() {} } /* usage */ SwiftSingleton.sharedInstance Singletons in IOS
27. Patterns protocol AnimationBehavior { func animate() } class ParallaxAnimationBehavior: AnimationBehavior { func animate() { println("Funky parallax animation code") } } Strategies
28. Patterns class AnimatingView: UIView { var animationBehavior: AnimationBehavior? override func viewDidLoad() { super.viewDidLoad() animationBehavior?.animate() } } Strategies
29. MVVM Decouples the View from the Model Moves the presentation logic out of the View Controller and into the View Model
30. MVVM Model App Data Controller Updates Model Controls View View User Presentation Human / Non-human View Model
31. MVVM import Foundation class Car { let make : String let model : String let date : NSDate init(make : String, model : String, date : NSDate) { self.make = make self.model = model self.date = date } } This is a simple model that might pop up in your app and it represents a Car Model
32. MVVM func displayCar() { let dateFormatter = NSDateFormatter() dateFormatter.dateFormat = "dd MMM yyyy" self.dateLabel.text = dateFormatter.stringFromDate(self.car.date) self.brandLabel.text = "\(self.car.make) \(self.car.model)" } Displaying a car in MVC
33. MVVM class CarViewModel { let car : Car let brandText : String let dateText : String init(car : Car) { self.car = car self.brandText = "\(self.car.make) \(self.car.model)" let dateFormatter = NSDateFormatter() dateFormatter.dateFormat = "dd MMM yyyy" self.dateText = dateFormatter.stringFromDate(self.car.date) } } If we have a Car view model
34. MVVM func displayCar() { self.nameLabel.text = self.viewModel.brandText; self.birthdateLabel.text = self.viewModel.dateText; } In our view controller
35. MVVM func testInitialization() { let car = Car() let carViewModel = CarViewModel(car: car) XCTAssertNotNil(carViewModel, "CarViewModel cannot be nil.") XCTAssertTrue(carViewModel.car === car, "Car should be equal to the car parameter") } Testing is convenient too
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