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The Bright Future of Swift
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The Future of Swift
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I can see clearly now, where Swift will go
I can see all obstacles in my way
Gone are the dark clouds that had me blind
It’s gonna be a bright, bright sun-shiny day.
- Johnny Nash (emphasis mine)
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Plan for the future,
but live in the present
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class Box {
let value: T
init(_ value: T) {
self.value = value
}
}
enum Result {
case Success(Box)
case Failure(Box)
}
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WWDC
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Plan for the future,
but live in the present
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Plan for the future,
but live in the present
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session.dataTaskWithURL(url) { (data, response, error) -> Void in
// process the response
}
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session.dataTaskWithURL(url) { (data, response, error) -> Void in
// process the response
dispatch_async(dispatch_get_main_queue()) {
// update UI
}
}
session.delegateQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
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func getBirds(completionHandler: [(Bird, UIImage)] -> Void) {
session.dataTaskWithURL(NSURL(string: "http://developer.apple.com/naming.json")!) {
(data, response, error) -> Void in
if let data = data, json = self.birdsJsonFromResponseData(data) {
var result: [(Bird, UIImage)] = []
for (index, bird) in json.enumerate() {
if let bird = self.parseBird(bird) {
self.getImage(bird) { image in
result.insert((bird, image), atIndex: min(result.count, index))
if result.count == json.count {
dispatch_async(dispatch_get_main_queue()) {
completionHandler(result)
}
}
}
}
}
}
}.resume()
}
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func getBirds(completionHandler: [(Bird, UIImage)] -> Void) {
session.dataTaskWithURL(NSURL(string: "http://developer.apple.com/naming.json")!) {
(data, response, error) -> Void in
if let data = data, json = self.birdsJsonFromResponseData(data) {
var result: [(Bird, UIImage)] = []
for (index, bird) in json.enumerate() {
if let bird = self.parseBird(bird) {
self.getImage(bird) { image in
result.insert((bird, image), atIndex: min(result.count, index))
if result.count == json.count {
dispatch_async(dispatch_get_main_queue()) {
completionHandler(result)
}
}
}
}
}
}
}.resume()
}
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Introducing Futures
(aka Promises)
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func getImage(name: String, completionHandler: UIImage -> Void)
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func getImage(name: String) -> Future
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getImage("swift").onSuccess { image in
// do something with the image
}
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getImage("swift").onSuccess { image in
// do something with the image
}.onSuccess { image in
// do something else with the image
}
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getImage("swift").onSuccess { image in
// do something with the image
}.onSuccess { image in
// do something else with the image
}.onFailure { error in
// handle the error
}
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func getImage(name: String) -> Future {
return Future { completion in
session.fetchImage(name, completionHandler: { image in
completion(.Success(image))
})
}
}
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getImage("swift").onSuccess { image in
// do something with the image
}.onSuccess { image in
// do something else with the image
}.onFailure { error in
// handle the error
}
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let image = getImage("swift")
// image is a Future
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let image = getImage("swift")
// image is a Future
image.zip(getDetails("swift")).onSuccess { image, details in
// do something with the image and the details
}
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let image = getImage("swift")
// image is a Future
image.zip(getDetails("swift")).onSuccess { image, details in
// do something with the image and the details
}.onFailure { error in
// deal with the error
}
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getDetails("swift")
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getDetails("swift").map { details in
return details.substringToIndex(
details.startIndex.advancedBy(30)
)
}
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getDetails("swift").map { details in
return details.substringToIndex(
details.startIndex.advancedBy(30)
)
}.map { summary in
return summary + "... Read more"
}
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getDetails("swift").map { details in
return details.substringToIndex(
details.startIndex.advancedBy(30)
)
}.map { summary in
return summary + "... Read more"
}
// subtitle is a Future
let subtitle =
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Asynchronous values
as first-class citizens
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getDetails("swift").map { details in
return details.substringToIndex(
details.startIndex.advancedBy(30)
)
}.map { summary in
return summary + "... Read more"
}
// subtitle is a Future
let subtitle =
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func +(lhs: Future, rhs: String) -> Future
getDetails("swift").map { details in
return details.substringToIndex(
details.startIndex.advancedBy(30)
)
}.map { summary in
return summary + "... Read more"
}
// subtitle is a Future
let subtitle =
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func +(lhs: Future, rhs: String) -> Future {
return lhs.map { l in
return l + rhs
}
}
getDetails("swift").map { details in
return details.substringToIndex(
details.startIndex.advancedBy(30)
)
}.map { summary in
return summary + "... Read more"
}
// subtitle is a Future
let subtitle =
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getDetails("swift").map { details in
return details.substringToIndex(
details.startIndex.advancedBy(30)
)
} + "... Read more"
func +(lhs: Future, rhs: String) -> Future {
return lhs.map { l in
return l + rhs
}
}
let subtitle =
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extension FutureType where Value == String {
func substringToIndex(index: Int) -> Future {
return map { str in
return str.substringToIndex(str.startIndex.advancedBy(index))
}
}
}
getDetails("swift").map { details in
return details.substringToIndex(
details.startIndex.advancedBy(30)
)
} + "... Read more"
let subtitle =
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getDetails("swift").substringToIndex(30) + "... Read more"
extension FutureType where Value == String {
func substringToIndex(index: Int) -> Future {
return map { str in
return str.substringToIndex(str.startIndex.advancedBy(index))
}
}
}
let subtitle =
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// subtitle is a Future
getDetails("swift").substringToIndex(30) + "... Read more"
let subtitle =
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cell.detailTextLabel!.text = subtitle
// subtitle is a Future
getDetails("swift").substringToIndex(30) + "... Read more"
let subtitle =
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public enum Optional
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The Future’s 20%
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func getImage(url: String) -> async UIImage
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func getImage(url: String) -> async UIImage {
let data: async NSData = session.fetch(url)
return UIImage(data: data)
}
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func setImage(url: String) -> async Void {
let image: async UIImage = getImage(url)
when let image = image {
imageView.image = image
}
}
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func setImage(url: String) -> Future {
let image: Future = getImage(url)
return image.onSuccess { image in
imageView.image = image
}.asVoid()
}
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func setImage(url: String) -> async Void {
let image: async UIImage = getImage(url)
when let image = image {
imageView.image = image
}
}
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func setImage(url: String) {
let image: async UIImage = getImage(url)
if let image = image {
imageView.image = image
}
}
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func setImage(url: String) {
let image: async UIImage = getImage(url)
imageView.image = image!
}
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The Future’s 20%
*
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The thread-safety layer
Copyable Reentrant Code Gateway Annotation
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@_semantics("swift.concurrent.launch")
func async(args: A, task: A -> Void) {
// launch the task
}
async(100, fibonacci)
The thread-safety layer
Copyable Reentrant Code Gateway Annotation
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Plan for the future,
but live in the present
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Thank you!
@thomvis88
https://github.com/Thomvis/BrightFutures
http://highstreetapp.com