Palestra sobre Controle de estados no CocoaheadsSP de 27/06/2017.

1. @BGONDIM
@BBILESCKY

2. ESTADODEFINIÇÃO, MANIPULAÇÃO E MANUTENÇÃO

3. CLASSES
> SIDE EFFECTS

4. VALUE TYPESTO THE RESCUE

5. IMUTABILIDADE
MUTÁVEL

6. struct Credential {
let username: String
let password: String
}

7. extension Credential {
func byChanging(username: String)-> Credential {
let newCredential = Credential(username: username, password: self.password)
return newCredential
}
func byChanging(password: String)-> Credential {
let newCredential = Credential(username: self.username, password: password)
return newCredential
}
}

8. struct Contact {
let firstName: String
let lastName: String
let email: String
let cellPhone: String?
let phone: String?
let birthdate: Date
let bloodType: BloodType
let hairColor: Color
let eyeColor: Color
let height: Int
let weight: Int
let nickname: String?
let spouse: Contact?
}

9. LET X VAR

10. FONTE ÚNICA DA
VERDADE

11. WILLSET
& DIDSET

12. SE A MUDANÇA
DE UM VALOR
AFETA OUTRO VALOR

13. ATUALIZE-O SEMPRE.

14. NÃO DEIXE PARA
O PROGRAMADORELE PODE NÃO SE LEMBRAR AMANHA OU DAQUI A 3 MESES

15. ENUM

16. DEFINIÇÃO CLARA
POSSIBILIDADES

17. ASSOCIATED VALUES

18. CASO PRÁTICO

19. APLICATIVO QUE EXIBE UMA LISTA DE
REPOSITÓRIOS DO GITHUB

20. class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {
@IBOutlet var tableView: UITableView!
var repositories: [String] = []
override func viewDidLoad() {
super.viewDidLoad()
tableView.dataSource = self
tableView.delegate = self
}
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return repositories.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "", for: indexPath)
return cell
}
}

21. O QUE SIGNIFICA
REPOSITORIES.COUNT == 0

22. NENHUM REQUEST RETORNOU DADOS AINDA
É O ESTADO INICIAL DA TELA
NÃO ENCONTRAMOS NENHUM DADO
OCORREU UM ERRO E NÃO FOI POSSÍVEL RECUPERAR DADOS

23. SOLUÇÕES?

24. VARIÁVEIS DE CONTROLE

25. private var listIsEmpty: Bool
private var currentRequest: Request?

26. NOVA FEATURE
ADICIONAR VIEWS PARA
BLANK/ERROR/LOADING

27. private var listIsEmpty: Bool
private var currentRequest: Request?
private var loadError: Error?
private var isLoading: Bool {
return currentRequest != nil
}

28. enum ViewState {
case willLoadInitialData
case loaded(repos:[String])
case loading(Request, oldRepos:[String])
case loadedWithError(repos:[String], Error)
case empty
}

29. var currentState: ViewState = .empty

30. var currentState: ViewState = .empty {
didSet {
render(old: oldState, newState: currentState)
}
}

31. var currentState: ViewState = .empty {
willSet {
handle(newState: currentState)
}
}

32. FEATURE REQUEST:
SELEÇÃO DE REPOSITÓRIO

33. enum ViewState {
case willLoadInitialData
case loaded(repos:[String], selected: String?)
case loading(Request, oldRepos:[String], selected: String?)
case loadedWithError(repos:[String], Error, selected: String?)
case empty
}

34. FEATURE REQUEST:
CANCELAR REQUEST ATUAL

35. extension ViewState {
var currentRequest: Request? {
guard let .loading(request, _, _) else { return nil }
return request
}
}
viewState.currentRequest?.cancel()

36. FEATURE REQUEST:
OFFLINE SUPPORT

37. enum ViewState {
case willLoadInitialData
case offline(repos:[String], changes: [Change], selected: String?)
case loaded(repos:[String], selected: String?)
case loading(Request, oldRepos:[String], selected: String?)
case loadedWithError(repos:[String], Error, selected: String?)
case empty
}

38. STATE CONTAINER

39. PERMITE MULTIPLAS ASSINATURAS
PARA MUDANÇAS DE VALOR

40. class State<Type> {
let key: String
var value: Type {
return __value
}
private var __value: Type
init(_ defaultValue: Type, key: String) {
self.__value = defaultValue
self.key = key
}
public func modify(_ value: Type) {
__value = value
didModify()
}
func didModify() {
}
}

41. protocol StateListener : AnyObject {
func stateModified<T>(_ state: State<T>)
}
protocol OptionalType {
var isNil: Bool { get }
}
extension Optional : OptionalType {
public var isNil: Bool {
return self == nil
}
}

42. class MonitoredState<Type> : State<Type> {
fileprivate let listeners: NSHashTable<AnyObject>
override init(_ defaultValue: Type, key: String) {
self.listeners = NSHashTable<AnyObject>.weakObjects()
super.init(defaultValue, key: key)
}
var allListeners: [StateListener] {
return self.listeners.allObjects.map({ $0 as? StateListener }).flatMap({ $0 })
}
override func didModify() {
super.didModify()
let allListeners = self.allListeners
let state = self
for l in allListeners {
l.stateModified(state)
}
}
func attach(listener: StateListener) {
self.listeners.add(listener as AnyObject)
}
}

43. class UserDefaultsState<Type> : MonitoredState<Type>, StateListener {
let innerState: MonitoredState<Type>
init(state: MonitoredState<Type>) {
self.innerState = state
super.init(state.value, key: state.key)
let existingValue = UserDefaults.standard.object(forKey: key)
if let existing = existingValue as? Type {
state.modify(existing)
} else if let data = existingValue as? Data, let decoded = NSKeyedUnarchiver.unarchiveObject(with: data) as? Type {
state.modify(decoded)
}
if let monitoredState = state as? MonitoredState<Type> {
monitoredState.attach(listener: self)
}
}
override var value: Type {
return innerState.value
}
override func modify(_ value: Type) {
innerState.modify(value)
}
func stateModified<T>(_ state: State<T>) {
self.didModify()
}
override func didModify() {
super.didModify()
let val = self.value
if let val = val as? OptionalType, val.isNil {
UserDefaults.standard.removeObject(forKey: self.key)
print("Removed (self.key) from UserDefaults")
} else if let val = val as? NSCoding {
UserDefaults.standard.set(NSKeyedArchiver.archivedData(withRootObject: val), forKey: self.key)
print("Saved (self.key) to UserDefaults")
} else {
UserDefaults.standard.set(val, forKey: self.key)
print("Saved (self.key) to UserDefaults")
}
UserDefaults.standard.synchronize()
}
}

44. class HistoryState<Type>: MonitoredState<Type>, StateListener {
let innerState: MonitoredState<Type>
private var __history: [Type] = []
public var history: [Type] {
return __history
}
override var value: Type {
return innerState.value
}
override func modify(_ value: Type) {
innerState.modify(value)
}
func stateModified<T>(_ state: State<T>) {
self.didModify()
}
init(state: MonitoredState<Type>) {
self.innerState = state
super.init(state.value, key: state.key)
if let monitoredState = state as? MonitoredState<Type> {
monitoredState.attach(listener: self)
}
}
override func didModify() {
super.didModify()
__history.append(self.value)
}
}

45. let appCount = MonitoredState<Int>(0, key: "appCount")

46. PERMITE A
PERSISTÊNCIA
DOS VALORES

47. let userDefaultsAppCount = UserDefaultsState(state: appCount)

48. TESTESHISTÓRICO DE ESTADOS

49. let historyAppCount = HistoryState(state: userDefaultsAppCount)

50. MAIS INFORMAÇÕES
MODELLING STATE IN SWIFT POR @JOHNSUNDELL
STATE CONTAINERS IN SWIFT POR

51. OBRIGADO