Swift: An Introduction to the Language

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Swift An introduction to the language

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Kris Arnold Shutterstock @wka @shuttertech

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Disclaimer The only people with more than a few months experience with Swift work at Apple

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Topics Language Design Principles Why a new language? Variables and Data Structures Flow Control Functions and Closures Classes and Protocols Structs and Enums Generics What Else? What's Missing? What's Next?

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Language Design Principles

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Language Design Principles Speed Safety Modern features Interoperability with Objective-C

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Why?

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Cruft

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No namespaces NSObject SSIImage

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nil NULL NSNull [NSNull null] NSNotFound Nil

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Variables and Data Structures

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var place = "World"

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var place = "World" println("Hello, \(place)")

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let place = "World" println("Hello, \(place)")

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let place = "World" println("Hello, \(place)") place = "North America" //error!

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var place = "World" println("Hello, \(place)") place = "North America"

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var place = "World"

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var place: String = "World"

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var cities = [String]()

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var cities = [String]() cities = ["New York", "Berlin"]

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var cities = [String]() var cities = ["New York", "Berlin"]

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var cities = ["New York", "Berlin"]

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var cities = ["New York", "Berlin"] cities[0] // "New York"

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var cities = ["New York", "Berlin"] cities[0] // "New York" cities.append("San Francisco")

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var cities = ["New York", "Berlin"] cities[0] // "New York" cities.append("San Francisco") cities.insert("Denver", atIndex: 0)

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var cities = ["New York", "Berlin"] cities[0] // "New York" cities.append("San Francisco") cities.insert("Denver", atIndex: 0) cities.count // 4

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var populations = [String: Int]()

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var populations = [String: Int]() populations = ["New York": 8_300_000, "Berlin": 3_500_000]

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var populations = [String: Int]() populations = ["New York": 8_300_000, "Berlin": 3_500_000] populations["Denver"] = 600_000 populations["San Francisco"] = 800_000

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var populations = [String: Int]() populations = ["New York": 8_300_000, "Berlin": 3_500_000] populations["Denver"] = 600_000 populations["San Francisco"] = 800_000 populations["New York"] // 8_300_000

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("nyc", 8_300_000)

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var nameAndPop = ("nyc", 8_300_000)

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var nameAndPop = ("nyc", 8_300_000) nameAndPop.0 // "nyc"

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var nameAndPop = (city: "nyc", population: 8_300_000)

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var nameAndPop = (city: "nyc", population: 8_300_000) nameAndPop.city // "nyc"

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Optionals

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var name: String

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var name: String var nickname: String?

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var name: String var nickname: String? name = nil // error

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var name: String var nickname: String? name = nil // error nickname = nil // OK

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populations["New York"]

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populations["New York"] // return type: Int?

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populations["New York"] // return type: Int? populations["Atlantis"] // return type: Int? // return value: nil

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Flow Control

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if … then … else for … in loops C-style for loops While loops Do-while loops

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var nickname: String?

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var nickname: String? … if let moniker = nickname { println("Hello \(moniker)") }

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var nickname: String? … if let moniker = nickname { println("Hello \(moniker)") } else { println("Hello friend") }

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var nickname: String? … println("Hello \(nickname!)")

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var nickname: String? …

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var nickname: String? … nickname?.extend(" :)")

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switch statements Demo

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Functions and Closures

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func sayHello() -> () { println "Hello" }

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func sayHello(name: String) -> () { println "Hello \(name)" }

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func sayHello(name: String) -> () { println "Hello \(name)" } sayHello("Lattner") // prints "Hello Lattner"

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func sayHello(name: String) -> () { println "Hello \(name)" } sayHello(name: "Lattner") // error!

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func sayHello(person name: String) -> () { println "Hello \(name)" } sayHello(person: "Lattner") // correct

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func sayHello(#name: String) -> () { println "Hello \(name)" } sayHello(name: "Lattner") // correct

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func sayHello(name: String = "You") -> () { println "Hello \(name)" }

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func sayHello(name: String) -> () { println "Hello \(name)" }

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func sayHello(firstName: String, lastName: String) -> () { println "Hello \(firstName) \(lastName)" }

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func sayHello(name: String) -> () { println "Hello \(name)" }

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func sayHello(name: String) -> (String) { return "Hello \(name)" }

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func sayHello(name: String) -> (String) { name += "!" return "Hello \(name)" }

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func sayHello(name: String) -> (String) { name += "!" // error! return "Hello \(name)" }

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func sayHello(var name: String) -> (String) { name += "!" return "Hello \(name)" }

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func sayHello(var name: String) -> (String) { name += "!" return "Hello \(name)" } var person = "Lattner" sayHello(person)

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func sayHello( name: String) -> (String) { name += "!" return "Hello \(name)" } var person = "Lattner" sayHello( person) println("Updated to \(person)") // "Updated to Lattner!"

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func sayHello(inout name: String) -> (String) { name += "!" return "Hello \(name)" } var person = "Lattner" sayHello(&person) println("Updated to \(person)") // "Updated to Lattner!"

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Closures

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var items = [100, 2, 75, 31, 99] items.sort // items is now [2, 31, 75, 99, 100]

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var items = [100, 2, 75, 31, 99] let sorter = { } items.sort(sorter)

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var items = [100, 2, 75, 31, 99] let sorter = { (num1: Int, num2: Int) } items.sort(sorter)

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var items = [100, 2, 75, 31, 99] let sorter = { (num1: Int, num2: Int) -> Bool in } items.sort(sorter)

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var items = [100, 2, 75, 31, 99] let sorter = { (num1: Int, num2: Int) -> Bool in } items.sort(sorter)

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var items = [100, 2, 75, 31, 99] let sorter = { (num1: Int, num2: Int) -> Bool in return num1 < num2 } items.sort(sorter)

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var items = [100, 2, 75, 31, 99] let sorter = { (num1: Int, num2: Int) -> Bool in return num1 < num2 } items.sort(sorter)

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var items = [100, 2, 75, 31, 99] let sorter = { (num1: Int, num2: Int) -> Bool in num1 < num2 } items.sort(sorter)

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var items = [100, 2, 75, 31, 99] let sorter = { (num1: Int, num2: Int) in num1 < num2 } items.sort(sorter)

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var items = [100, 2, 75, 31, 99] let sorter = { (num1, num2) in num1 < num2 } items.sort(sorter)

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var items = [100, 2, 75, 31, 99] items.sort({(num1, num2) in num1 < num2})

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var items = [100, 2, 75, 31, 99] items.sort({ num1, num2 in num1 < num2})

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var items = [100, 2, 75, 31, 99] items.sort({ $0 < $1 })

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var items = [100, 2, 75, 31, 99] items.sort({ $0 < $1 })

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var items = [100, 2, 75, 31, 99] items.sort { $0 < $1 }

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let list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] let evens = list.filter { $0 % 2 == 0 }

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let list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] let evens = list.filter { $0 % 2 == 0 } let tenX = list.map { $0 * 10 }

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let list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] let evens = list.filter { $0 % 2 == 0 } let tenX = list.map { $0 * 10 } let sum = list.reduce(0) { $0 + $1 }

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func makeMultiplier(number: Int) -> Int -> (Int) { }

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func makeMultiplier(number: Int) -> Int -> (Int) { }

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func makeMultiplier(number: Int) -> Int -> (Int) { let multiplier = { } }

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func makeMultiplier(number: Int) -> Int -> (Int) { let multiplier = { (given: Int) -> Int in return number * given } }

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func makeMultiplier(number: Int) -> Int -> (Int) { let multiplier = { (given: Int) -> Int in return number * given } return multiplier }

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func makeMultiplier(number: Int) -> Int -> (Int) { let multiplier = { (given: Int) -> Int in return number * given } return multiplier } let timesTwenty = makeMultiplier(20)

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func makeMultiplier(number: Int) -> Int -> (Int) { let multiplier = { (given: Int) -> Int in return number * given } return multiplier } let timesTwenty = makeMultiplier(20) timesTwenty(3) // output == 60

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let priority = DISPATCH_QUEUE_PRIORITY_BACKGROUND let queue = dispatch_get_gloabl_queue(priority, 0)

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let priority = DISPATCH_QUEUE_PRIORITY_BACKGROUND let queue = dispatch_get_gloabl_queue(priority, 0) dispatch_async(queue) { longRunningOperation() longerRunningOperation() }

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let priority = DISPATCH_QUEUE_PRIORITY_BACKGROUND let queue = dispatch_get_gloabl_queue(priority, 0) dispatch_async(queue) { longRunningOperation() longerRunningOperation() }

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Classes and Protocols

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class Image { }

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class Image { var mediaId = 0 var description = "My awesome image" }

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class Image { var mediaId = 0 var description = "My awesome image" } var myImage = Image() myImage.mediaId = 200_000

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class Image { var mediaId var description }

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class Image { var mediaId :Int var description :String }

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class Image { var mediaId :Int var description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description } }

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class Image { var mediaId :Int var description :String init(mediaId: Int, description: String) { self.mediaId = mediaId } }

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class Image { var mediaId :Int var description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description } }

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class Image { var mediaId :Int var description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description } func approveImage() -> () { println("Approving…") } }

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var myImage = Image( mediaId: 200_000, description: "Testing" )

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var myImage = Image( mediaId: 200_000, description: "Testing" ) println("the description for \(myImage.mediaId) is \(myImage.description)")

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var myImage = image( mediaId: 200_000, description: "Testing" ) println("the description for \(myImage.mediaId) is \(myImage.description)") myImage.approveImage()

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var myImage = image( mediaId: 200_000, description: "Testing" ) println("the description for \(myImage.mediaId) is \(myImage.description)") myImage.approveImage() myImage.description = betterDescription

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class Image { var mediaId :Int var description :String //… }

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class Image { var mediaId :Int var description :String { } //… }

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class Image { var mediaId :Int var description :String { didSet { } } //… }

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class Image { var mediaId :Int var description :String { didSet { println("Changed desc to \(description)") updateAuditTrail(mediaId, description) } } //… }

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class Image { var mediaId :Int var description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description } }

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class Image { let mediaId :Int let description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description } }

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class Image { let mediaId :Int let description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description } } //… image.description = betterDescription // error!

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class Image { var mediaId :Int var description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description } }

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class Image { var mediaId :Int var description :String var height :Int var width :Int … }

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class Image { var mediaId :Int var description :String var height :Int var width :Int var aspectRatio :Float … }

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class Image { var mediaId :Int var description :String var height :Int var width :Int var aspectRatio :Float { return Float(height) / Float(width) } … }

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class Image { var mediaId :Int var description :String var height :Int var width :Int var aspectRatio :Float { return Float(height) / Float(width) } … }

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class Image { var mediaId :Int var description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description } }

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class Image: Media { var mediaId :Int var description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description } }

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class Image: Media { var mediaId :Int var description :String init(mediaId: Int, description: String) { super.init() // error! self.mediaId = mediaId self.description = description } }

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class Image: Media { var mediaId :Int var description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description super.init() // correct! } }

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class Image: Media { var mediaId :Int var description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description super.init() // correct! } func upload() -> () { println("Uploading…") } }

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class Image { var mediaId :Int var description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description super.init() // correct! } func upload() -> () { println("Uploading…") } }

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final class Image { var mediaId :Int var description :String init(mediaId: Int, description: String) { self.mediaId = mediaId self.description = description super.init() // correct! } func upload() -> () { println("Uploading…") } }

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class Image { var mediaId :Int var description :String //… func upload() -> () { println("Uploading…") } }

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class Image { var mediaId :Int private var description :String //… private func upload() -> () { println("Uploading…") } }

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private class Image { var mediaId :Int private var description :String //… private func upload() -> () { println("Uploading…") } }

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internal class Image { var mediaId :Int internal var description :String //… private func upload() -> () { println("Uploading…") } }

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Extensions

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extension Image { }

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extension Image { func supersize () -> (UIImage) { // do scaling here } }

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Protocols

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class Uploader { }

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class Uploader { func upload(uploadee: Media) { } }

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class Uploader { func upload(uploadee: Media) { uploadee.uploadInProgress() doHTTPUpload(source: uploadee.filePath, destination: uploadee.fileName) uploadee.uploadComplete() } }

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class Uploader { func upload(uploadee: Media) { uploadee.uploadInProgress() doHTTPUpload(source: uploadee.filePath, destination: uploadee.fileName) uploadee.uploadComplete() } }

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class Uploader { func upload(uploadee: Media) { uploadee.uploadInProgress() doHTTPUpload(source: uploadee.filePath, destination: uploadee.fileName) uploadee.uploadComplete() } }

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class Uploader { func upload(uploadee: Media) { uploadee.uploadInProgress() doHTTPUpload(source: uploadee.filePath, destination: uploadee.fileName) uploadee.uploadComplete() } }

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class Uploader { func upload(uploadee: Media) { uploadee.uploadInProgress() doHTTPUpload(source: uploadee.filePath, destination: uploadee.fileName) uploadee.uploadComplete() } func doHTTPUpload(#source: String, #destination: String) -> () { // hand-waving… } }

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class Media { var mediaId: Int = 200_000 var filePath: String = "/tmp/media.jpg" var fileType: String = "jpg" var fileName: String { return String(mediaId) + "." + fileType } func uploadInProgress() -> () { // do stuff } func uploadComplete() -> () { // do stuff } }

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protocol Uploadable { }

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protocol Uploadable { var filePath: String { get } var fileName: String { get } }

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protocol Uploadable { var filePath: String { get } var fileName: String { get } func uploadInProgress() -> () func uploadComplete() -> () }

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class Uploader { func upload(uploadee: Uploadable) { uploadee.uploadInProgress() doHTTPUpload(source: uploadee.filePath, destination: uploadee.fileName) uploadee.uploadComplete() } func doHTTPUpload(#source: String, #destination: String) -> () { // hand-waving… } }

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class Media: Uploadable { var mediaId: Int = 200_000 var filePath: String = "/tmp/media.jpg" var fileType: String = "jpg" var fileName: String { return String(mediaId) + "." + fileType } func uploadInProgress() -> () { // do stuff } func uploadComplete() -> () { // do stuff } }

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class CSV: Uploadable { // … }

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Structs and Enums

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struct CGPoint { CGFloat x; CGFloat y; };

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struct CGPoint { CGFloat x; CGFloat y; }; struct CGSize { CGFloat width; CGFloat height; };

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struct CGPoint { CGFloat x; CGFloat y; }; struct CGSize { CGFloat width; CGFloat height; }; struct CGRect { CGPoint origin; CGSize size; };

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struct CGPoint { CGFloat x; CGFloat y; }; struct CGSize { CGFloat width; CGFloat height; }; struct CGRect { CGPoint origin; CGSize size; }; 16.67

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CGPointMake CGRectMake CGSizeMake CGRectDivide CGRectInset CGRectIntegral CGRectIntersection CGRectOffset CGRectUnion CGPointEqualToPoint CGSizeEqualToSize CGRectEqualToRect CGRectIntersectsRect CGRectContainsPoint CGRectContainsRect CGRectGetMinX CGRectGetMinY CGRectGetMidX CGRectGetMidY CGRectGetMaxX CGRectGetMaxY CGRectGetHeight CGRectGetWidth CGRectIsEmpty CGRectIsNull CGRectIsInfinite

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struct Image { }

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struct Image { var mediaId: Int var description: String }

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struct Image { var mediaId: Int var description: String func upload() -> () { println("Uploading image \(self.mediaId)") } }

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struct Image { var mediaId: Int var description: String func upload() -> () { println("Uploading image \(self.mediaId)") } } var myImage = Image(mediaId: 200_000, description: "test")

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struct Image { var mediaId: Int var description: String func upload() -> () { println("Uploading image \(self.mediaId)") } } var myImage = Image(mediaId: 200_000, description: "test") myImage.upload()

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struct Image { var mediaId: Int var description: String func upload() -> () { println("Uploading image \(self.mediaId)") } func bang() -> () { self.description.extend("!") } }

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struct Image { var mediaId: Int var description: String func upload() -> () { println("Uploading image \(self.mediaId)") } mutating func bang() -> () { self.description.extend("!") } }

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Should I use a struct or a class?

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var imageStruct = imageStr(mediaId: 200_000, description: "Flowers") var newImageStruct = imageStruct

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var imageStruct = imageStr(mediaId: 200_000, description: "Flowers") var newImageStruct = imageStruct imageStruct.description = "Kittens"

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var imageStruct = imageStr(mediaId: 200_000, description: "Flowers") var newImageStruct = imageStruct imageStruct.description = "Kittens" println(\(newImaegStruct.description)) // prints "Flowers"

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var imageStruct = imageStr(mediaId: 200_000, description: "Flowers") var newImageStruct = imageStruct imageStruct.description = "Kittens" println(\(newImaegStruct.description)) // prints "Flowers" var imageObject = imageObj(mediaId: 200_000, description: "Flowers") var newImageObject = imageObject

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Enums

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enum Orientation { }

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enum Orientation { case Portrait case Landscape case Square }

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struct Image { var mediaId: Int var description: String }

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struct Image { var mediaId: Int var description: String var orientation: Orientation }

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struct Image { var mediaId: Int var description: String var orientation: Orientation } var myImage = Image( mediaId: 200_000, description: "Test", orientation: Orientation.Landscape )

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struct Image { var mediaId: Int var description: String var orientation: Orientation } var myImage = Image( mediaId: 200_000, description: "Test", orientation: Orientation.Landscape )

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struct Image { var mediaId: Int var description: String var orientation: Orientation } var myImage = Image( mediaId: 200_000, description: "Test", orientation: .Landscape )

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enum Orientation { case Portrait case Landscape case Square }

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enum Orientation { case Portrait case Landscape case Square func describe () -> () { } }

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enum Orientation { case Portrait case Landscape case Square func describe () -> () { switch self { } } }

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enum Orientation { case Portrait case Landscape case Square func describe () -> () { switch self { case .Portrait: println("Portrait orientation") case .Landscape: println("Landscape orientation") case .Square: println("What is this, Instagram?") } } }

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struct Image { enum Orientation { case Portrait case Landscape case Square } var mediaId: Int var description: String var orientation: Orientation }

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Generics

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struct Lightbox { var items: [Image] mutating func addItem(item: Image) -> () { self.items.append(item) } mutating func merge(other: Lightbox) -> () { for item in other.items { self.addItem(item) } } }

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struct Clipbox { var items: [Video] mutating func addItem(item: Video) -> () { self.items.append(item) } mutating func merge(other: Clipbox) -> () { for item in other.items { self.addItem(item) } } }

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struct Clipbox { var items: [Video] mutating func addItem(item: Video) -> () { self.items.append(item) } mutating func merge(other: Clipbox) -> () { for item in other.items { self.addItem(item) } } }

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struct Mediabox { }

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struct Mediabox { var items: [T] }

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struct Mediabox { var items: [T] = [] mutating func addItem(item: T) -> () { self.items.append(item) } mutating func merge(other: Mediabox) -> () { for item in other.items { self.addItem(item) } } }

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var myLightbox = Mediabox() myLightbox.addItem(flowerImage) myLightbox.addItem(kittenImage) var myClipbox = Mediabox() myClipbox.addItem(surferVid) myClipbox.addItem(skierVid) myLightbox.addItem(surferVid) //error! myClipbox.merge(other: myLightbox) //error!

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What Else?

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@autoclosure automatic reference counting avoiding circular references with the weak keyword variadic parameters closed vs. open ranges associated and raw values for Enums where clauses in generics the Swift standard library operator overloading sequences and generators typealias type casting AnyObject calling Objective-C from Swift calling Swift from Objective-C