CocoaHeads SKG #8 - Application Architecture

Transcript

1. iOS Application
   Architecture
   Part One
   CocoaheadsSKG Dimitri James Tsiflitzis
   

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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
   

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3. Light View Controllers
   

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4. Apple MVC
   Model
   App Data
   Controller
   Updates Model
   Controls View
   View
   User
   Presentation
   Human / Non-human
   

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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
   

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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
   

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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
   }
   }
   

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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
   

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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
   }
   }
   

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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
    

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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
    

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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
    

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13. Container & Child View Controllers
    Adding a container view controller in Interface Builder
    View Controller
    Container
    

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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
    

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15. Communication
    

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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
    

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17. Interlude: Objective-C Categories, Extensions
    and Swift extensions.
    Airport
    Airport.m
    Airport+Runway.m
    

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18. Interlude: Objective-C Categories, Extensions
    and Swift extensions.
    extension SomeClass {
    /* add new functionality here */
    }
    

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19. Notification Centre
    NSNotificationCenter.defaultCenter().postNotificationName("notificationReceived", object: nil)
    This is how you post an NSNotification.
    

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20. Notification Centre
    NSNotificationCenter.defaultCenter().addObserver(self,
    selector:#selector(notificationReceived(_:)), name: notificationReceived, object: nil)
    This is how you observe an NSNotification
    

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21. Notification Centre
    func receiveNotification(notification : NSnotification) {
    }
    And of course, you’ll need to define the method that will be executed.
    

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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
    

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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) {
    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)
    }
    }
    

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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
    

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25. Patterns
    

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26. Patterns
    /* definition */
    class SwiftSingleton {
    static let sharedInstance = SwiftSingleton()
    private init() {}
    }
    /* usage */
    SwiftSingleton.sharedInstance
    Singletons in IOS
    

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27. Patterns
    protocol AnimationBehavior {
    func animate()
    }
    class ParallaxAnimationBehavior: AnimationBehavior {
    func animate() {
    println("Funky parallax animation code")
    }
    }
    Strategies
    

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28. Patterns
    class AnimatingView: UIView {
    var animationBehavior: AnimationBehavior?
    override func viewDidLoad() {
    super.viewDidLoad()
    animationBehavior?.animate()
    }
    }
    Strategies
    

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29. MVVM
    Decouples the View from the Model
    Moves the presentation logic out of the View Controller and into
    the View Model
    

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30. MVVM
    Model
    App Data
    Controller
    Updates Model
    Controls View
    View
    User
    Presentation
    Human / Non-human
    View
    Model
    

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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
    

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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
    

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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
    

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34. MVVM
    func displayCar() {
    self.nameLabel.text = self.viewModel.brandText;
    self.birthdateLabel.text = self.viewModel.dateText;
    }
    In our view controller
    

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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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36. Ευχαριστούμε
    

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