This document discusses delegateless coordinators as an alternative approach to managing view controller responsibilities and navigation flow in iOS applications. It begins by outlining common problems with the traditional MVC pattern, such as managing dependencies, data fetching, and navigation logic. It then introduces coordinators as objects that can manage view controllers and take responsibility for navigation flow. The document discusses using delegation and the chain of responsibility patterns to implement coordinator logic. It proposes defining coordinator protocols and base classes to handle events without requiring view controller delegates. Overall, the document proposes an approach using coordinator objects and protocols to improve separation of concerns in iOS apps compared to traditional MVC.

2. Delegateless
Coordinators
Ou ainda… Event Based Coordinators

3. SUMÁRIO
Conteúdo
●Problemas do MVC
●Introdução aos Coordinators
●Delegation
●Solução Base
●Chain of Responsibility
●Delegateless Coordinators

4. Problemas do
MVC

5. Problemas do MVC
Responsabilidades
Dependency Injection
Navigation Flow
• Layout
• Model-View binding
• Subview management
• User Input/Interaction
• Data
• Fetching
• Transformation
• Persistency
• Error Handling
• Navigation Flow

6. Problemas do MVC
Responsabilidades
Dependency Injection
Navigation Flow
• Core Data/Realm
• Network
• Cache
• SomethingManager
• Frameworks de DI
• Typhon
• Kraken
• Perform
• SwiftDependencyInjection
• Swinject

7. Problemas do MVC
Responsabilidades
Dependency Injection
Navigation Flow

8. Problemas do MVC
Responsabilidades
Dependency Injection
Navigation Flow
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier !== "showDetail" {
if let indexPath = tableView.indexPathForSelectedRow {
let object = fetchedResultsController.object(at: indexPath)
let controller = (segue.destination as! UINavigationController)
.topViewController as! DetailViewController
controller.detailItem = object
controller.navigationItem
.leftBarButtonItem = splitViewController!?.displayModeButtonItem
controller.navigationItem
.leftItemsSupplementBackButton = true
}
}
}

9. Introdução aos
Coordinators

10. So what is a coordinator?
The Coordinator is a PONSO, like all great objects. For
something like Instagram’s photo creation flow, we could
have a PhotoCreationCoordinator. The app
coordinator could spawn a new one, and pass it the
root view controller so that it could present the first
view controller in the flow.
The Coordinator
(Soroush Khanlou)

11. So what is a coordinator?
A coordinator is an object that bosses one or more view
controllers around. Taking all of the driving logic out of
your view controllers, and moving that stuff one layer
up is gonna make your life a lot more awesome.
Coordinators Redux
(Soroush Khanlou)

12. Estrutr

13. Delegation

14. Delegation
Delegation is a way to make composition as powerful for reuse as inheritance.
In delegation, two objects are involved in handling a request: a receiving object
delegates operations to its delegate. This is analogous to subclasses deferring
requests to parent classes. But with inheritance, an inherited operation can
always refer to the receiving object through the this member variable in C++
and self in Smalltalk. To achieve the same effect with delegation, the receiver
passes itself to the delegate to let the delegated operation refer to the receiver.

15. Delegation: Super Máquina e RoboCop
Let’s start with a story: Once upon a time, there was a man with no name.
Knight Industries decided that if this man were given guns and wheels and
booster rockets, he would be the perfect crime-fighting tool. First they
thought, “Let’s subclass him and override everything we need to add the
guns and wheels and booster rockets.” The problem was that to subclass
Michael Knight, they needed to wire his insides to the guns, wheels, and
booster rockets – a time-consuming task requiring lots of specialized
knowledge. So instead, Knight Industries created a helper object, the
Knight Industries 2000, or “KITT,” a well-equipped car designed to assist
Michael Knight in a variety of crime- fighting situations.

16. Delegation: Super Máquina e RoboCop
While approaching the perimeter of an arms dealer’s compound, Michael
Knight would say, “KITT, I need to get to the other side of that wall.” KITT
would then blast a big hole in the wall with a small rocket. After destroying
the wall, KITT would return control to Michael, who would charge through
the rubble and capture the arms dealer.
Note how creating a helper object is different from the RoboCop
approach. RoboCop was a man subclassed and extended. The RoboCop
project involved dozens of surgeons who extended the man into a fighting
machine. This is the approach taken by many object-oriented frameworks.

17. Delegation: Super Máquina e RoboCop
In the Cocoa framework, many objects are extended in the Knight
Industries way – by supplying them with helper objects. In this section, you
are going to provide the speech synthesizer with a type of helper object
called a delegate.
From Cocoa Programming for OS X: The Big Nerd Ranch Guide

18. MVC-C · Injecting
Coordinator pattern in
UIKit
Taking the first step towards clean and minimal
app architecture in iOS app means freeing your
view controllers from the burden of dealing with
other controllers.

19. Implementação extension UIViewController {
private struct AssociatedKeys {
static var ParentCoordinator = "ParentCoordinator"
}
public weak var parentCoordinator: Coordinating? {
get {
return objc_getAssociatedObject(self,
&AssociatedKeys.ParentCoordinator) as? Coordinating
}
set {
objc_setAssociatedObject(self,
&AssociatedKeys.ParentCoordinator,
newValue,
.OBJC_ASSOCIATION_ASSIGN)
}
}
}
View Controller
UIResponder
UIEvent
Filhos de UIResponder
Documentação

20. Implementação extension UIResponder {
public var coordinatingResponder: UIResponder? {
return next
}
}
extension UIResponder {
func messageTemplate(args: Whatever, sender: Any?) {
coordinatingResponder!?.messageTemplate(args: args, sender: sender)
}
}
extension UIResponder {
func cartBuyNow(_ product: Product, sender: Any?) { … }
func cartAdd(product: Product, color: ColorBox,
sender: Any?, completion: @escaping (Bool, Int) !-> Void) { … }
}
View Controller
UIResponder
UIEvent
Filhos de UIResponder
Documentação

21. Implementação
Responder objects—that is, instances of UIResponder—
constitute the event-handling backbone of a UIKit app.
Many key objects are also responders, including the
UIApplication object, UIViewController objects, and all
UIView objects (which includes UIWindow). As events
occur, UIKit dispatches them to your app's responder
objects for handling.
View Controller
UIResponder
UIEvent
Filhos de UIResponder
Documentação

22. Implementação
In addition to handling events, UIKit responders also
manage the forwarding of unhandled events to other
parts of your app. If a given responder does not
handle an event, it forwards that event to the next
event in the responder chain. UIKit manages the
responder chain dynamically, using predefined rules to
determine which object should be next to receive an
event. For example, a view forwards events to its
superview, and the root view of a hierarchy forwards
events to its view controller.
View Controller
UIResponder
UIEvent
Filhos de UIResponder
Documentação

23. Implementação
View Controller
UIResponder
UIEvent
Filhos de UIResponder
Documentação

24. Implementação
View Controller
UIResponder
UIEvent
Filhos de UIResponder
Documentação

25. Implementação
View Controller
UIResponder
UIEvent
Filhos de UIResponder
Documentação

26. Implementação
View Controller
UIResponder
UIEvent
Filhos de UIResponder
Documentação

27. Implementação
View Controller
UIResponder
UIEvent
Filhos de UIResponder
Documentação

28. Implementação
•open class UIView : UIResponder
•open class UIViewController : UIResponder
•open class UIWindow : UIView
•class AppDelegate: UIResponder
•open class UIApplication : UIResponder
View Controller
UIResponder
UIEvent
Filhos de
UIResponder
Documentação

29. Chain of
Responsibility

30. Chain-of-Responsibility
In object-oriented design, the chain-of-responsibility pattern is a design pattern
consisting of a source of command objects and a series of processing objects.
Each processing object contains logic that defines the types of command
objects that it can handle; the rest are passed to the next processing object in
the chain. A mechanism also exists for adding new processing objects to the end
of this chain. Thus, the chain of responsibility is an object oriented version of
the if ... else if ... else if ....... else ... endif idiom, with the benefit that the
condition–action blocks can be dynamically rearranged and reconfigured at
runtime.

31. Delegateless
Coordinators
Nossa solução

32. There are several kinds of events, including touch
events, motion events, remote-control events, and
press events. To handle a specific type of event, a
responder must override the corresponding
methods. For example, to handle touch events, a
responder implements the touchesBegan(_:with:),
touchesMoved(_:with:), touchesEnded(_:with:), and
touchesCancelled(_:with:) methods. In the case of
touches, the responder uses the event information
provided by UIKit to track changes to those touches
and to update the app's interface appropriately.
Remembering Events
Initial Concept
Defining Events
Protocol
Base implementation
Child management
Event handling

33. protocol ActionType {}
struct ResponseAction {
var type: ActionType
}
class Action {
private var target: NSObject?
private var selector: Selector?
func addTarget(_ target: NSObject?, action: Selector) {
self.target = target
self.selector = action
}
func send(_ event: Any) {
target!?.perform(selector, with: event)
}
}
Remembering Events
Initial Concept
Defining Events
Protocol
Base implementation
Child management
Event handling

34. class MyCoodinator: NSObject {
let action: Action
override init() {
action = Action()
super.init()
action.addTarget(self, action: #selector(self.navigate(to:)))
}
@objc func navigate(to destination: Any) {
guard let value = destination as? ResponseAction,
let type = value.type as? HomeType else {
return
}
print(type)
}
}
Remembering Events
Initial Concept
Defining Events
Protocol
Base implementation
Child management
Event handling

35. protocol AppEventType { }
protocol AppEventSubType { }
protocol AppEvent {
var type: AppEventType { get }
var subtype: AppEventSubType? { get }
}
Remembering Events
Initial Concept
Defining Events
Protocol
Base implementation
Child management
Event handling

36. protocol CoordinatorProtocol: class {
var identifier: String { get }
var parent: CoordinatorProtocol? { get set }
var childCoordinators: [String: CoordinatorProtocol] { get }
func canProcessEvent(_ event: AppEvent,
withSender sender: Any?) !-> Bool
func target(forEvent event: AppEvent,
withSender sender: Any?) !-> CoordinatorProtocol?
func handleEvent(_ event: AppEvent, withSender: Any?)
func start(with completion: @escaping () !-> Void)
func stop(with completion: @escaping () !-> Void)
func startChild(coordinator: CoordinatorProtocol,
completion: @escaping () !-> Void)
func stopChild(coordinator: CoordinatorProtocol,
completion: @escaping () !-> Void)
}
Remembering Events
Initial Concept
Defining Events
Protocol
Base implementation
Child management
Event handling

37. class Coordinator: NSObject, CoordinatorProtocol {
weak var parent: CoordinatorProtocol?
var childCoordinators: [String: CoordinatorProtocol] = [:]
weak var rootViewController: UIViewController?
init(rootViewController: UIViewController) {
self.rootViewController = rootViewController
}
func start(with completion: @escaping () !-> Void = {}) {
self.rootViewController!?.parentCoordinator = self
completion()
}
func stop(with completion: @escaping () !-> Void = {}) {
rootViewController!?.parentCoordinator = nil
completion()
}
Remembering Events
Initial Concept
Defining Events
Protocol
Base implementation
Child management
Event handling

38. func startChild(coordinator: CoordinatorProtocol,
completion: @escaping () !-> Void) {
childCoordinators[coordinator.identifier] = coordinator
coordinator.parent = self
}
func stopChild(coordinator: CoordinatorProtocol,
completion: @escaping () !-> Void = {}) {
coordinator.parent = nil
coordinator.stop { [unowned self] in
self.childCoordinators
.removeValue(forKey: coordinator.identifier)
completion()
}
}
Remembering Events
Initial Concept
Defining Events
Protocol
Base implementation
Child management
Event handling

39. func canProcessEvent(_ event: AppEvent,
withSender sender: Any?) !-> Bool {
return false
}
func target(forEvent event: AppEvent,
withSender sender: Any?) !-> CoordinatorProtocol? {
guard self.canProcessEvent(event,
withSender: sender) !!= true else {
return self
}
var next = self.parent
while next!?.canProcessEvent(event,
withSender: sender) !!= true {
next = next!?.parent
}
return next
}
func handleEvent(_ event: AppEvent, withSender sender: Any?) {
if self.canProcessEvent(event, withSender: sender) {
!//do something
}
else {
let handler = self.target(forEvent: event,
withSender: sender)
handler!?.handleEvent(event, withSender: sender)
}
}
Remembering Events
Initial Concept
Defining Events
Protocol
Base implementation
Child management
Event handling

40. DEMO TIME
See here:
https://github.com/talesp/DelegatelessCoordinators

41. Centro
Av. Presidente Wilson,
231 - 29º andar
(21) 2240-2030
Cidade Monções
Av. Nações Unidas,
11.541 - 3º andar
(11) 4119-0449
Savassi
Av. Getúlio Vargas, 671
Sala 800 - 8º andar
(31) 3360-8900
www.concrete.com.br