conf.cocoaheads.by 2015

1. Presenting things in Swift

2. // Disposable.swift
// ReactiveCocoa
/// Represents something that can be “disposed,” usually
/// associated with freeing resources or canceling work.
public protocol Disposable {
/// Whether this disposable has been disposed already.
var disposed: Bool { get }
func dispose()
}

3. func present<Value>(value: Value) -> ()
func present<Value>(sink: Value -> ()) -> Disposable
func present<ViewModel>(viewModel: ViewModel) -> Disposable
Presenter

4. func present<T>(value: T) -> Disposable?
Presenter

5. // UIKit+Helpers.swift
extension UILabel {
var textPresenter: Presenter<String> {
return Presenter.UI { [weak self] in
self?.text = $0
return nil
}
}
}

6. // UIKit+Helpers.swift
extension UITextField {
var textSinkPresenter: Presenter<String -> ()> {
return Presenter.UI { sink in
let textDidChangeObserver = NSNotificationCenter
.defaultCenter()
.addObserverForName(
UITextFieldTextDidChangeNotification,
object: self,
queue: NSOperationQueue.mainQueue(),
usingBlock: { [weak self] _ in
if let query = self?.text {
sink(query)
}
}
)
return ActionDisposable {
NSNotificationCenter
.defaultCenter()
.removeObserver(textDidChangeObserver)
}
}
}
}

7. // ViewModel+Presenters.swift
struct Presenter<T> {
private let bind: T -> Disposable?
func present(value: T) -> Disposable? {
return bind(viewModel)
}
private init(_ bind: T -> Disposable?) {
self.bind = bind
}
}

8. // ViewModel+Presenters.swift
extension Presenter {
static func UI(bind: T -> Disposable?) -> Presenter {
return Presenter { viewModel in
let disposable = CompositeDisposable()
disposable += UIScheduler().schedule {
disposable += bind(viewModel)
}
return disposable
}
}
}

9. when("user enters a valid number") {
beforeEach {
outputs = sut(Model.mock())
outputs.phoneSink()?("4234567890")
}
then("next button is active") {
expect(outputs.nextActive()).to(beTrue())
}
}

10. // ViewModel+Presenter.swift
extension Presenter {
static func Test(handler: ViewModel -> Disposable?) -> Presenter {
if (nil == NSClassFromString("XCTestCase")) {
assertionFailure()
return Presenter { _ in nil }
}
return Presenter(handler)
}
}

11. then("placeholder is correct") {
expect(outputs.password()?.placeholder.lastValue)
.to(beLocalized(forKey: .ScreenSignUpPasswordPlaceholder))
}

12. In other words
• ViewModel is *pure* ViewController
• Presenters are bindings with benefits
• View is: styles, animations etc.

13. thanks!