CocoaheadsSKG #1 - Introduction to Swift

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Introduction to Swift Part One Dimitri James Tsiflitzis CocoaHeadsSKG

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About Swift ● Safety ● Support Cocoa and Cocoa Touch ● Works side by side with Objective-C code ● Single implementation file ● Error handling, closures, multiple return values, functional programming patterns, generics, fast iteration etc. etc. etc.

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Hello world in Objective-C #import int main(void) { NSLog(@"Hello, world!\n"); return 0; }

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Hello world in Swift print(“Hello World!”)

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Variables and Constants var meetupName : String = “CocoaHeads” var version : Int = 3 // mutable meetupName = “CocoaHeadsSKG” let meetupCity : String = “Thessaloniki” // immutable meetupCity = “Athens” // error

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Variables and Constants var meetupName = “CocoaHeads” // String var version = 3 // Int let meetupCity = “Athens” // String let isSummer = true // Bool let π = 3.14 // Double let = " "

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Type aliases Type aliases define an alternative name for an existing type. You define type aliases with the typealias keyword.

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Type aliases typealias AudioSample = UInt16 var maxAmplitudeFound = AudioSample.min // maxAmplitudeFound is now 0”

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Type aliases typealias Position = (x: Int, y: Int) // method “overloading”, illegal in obj-c func takePosition(x: Int, y: Int) { } func takePosition(position: Position) { } takePosition(100, y: 100) takePosition(Position(x: 200, y: 100))

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String let myString = “I am a String” // inferred let theirString = myString + “!” let a = 5 let aString = “a is \(a)” // printed as “a is 5”

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Collection Literals var names = [“Eleni”, “Giannis”, “Luke”] var names: [String] = [“Eleni”, “Giannis”, “Luke”] var names: Array = [“Eleni”, “Giannis”, “Luke”] var numberOfiPhones = [“Eleni”: 2, ”Luke”:0] var d: Dictionary< String, Int> = [“key1”: 1, ”key2”:2] var d: [String: Int] = [“key1”: 1, ”key2”:2]

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Loops while !ending { print(“looping”) } for var i = 0; i < 10; i++ { print(i) } for number in 0...3 { print(“number \(number)” }

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Loops // dictionary literal + tuple for (aKey, aValue) in [“Eleni”: 2, ”Luke”:0] { print(“aKey \(aKey) aValue \(aValue)” }

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Arrays var aList = [“item0”, “item1”]; aList += “item3” aList += [“item4”, “item5”] aList[1] = “listItem1”

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Dictionaries var numberOfiPhones = [“Eleni”: 2, ”Luke”:0] numberOfiPhones[“Luke”] = 1 var vadersPhones = numberOfiPhones[“vader”] // nil // vadersPhones is an Optional

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Optionals You use optionals in situations where a value may be absent. An optional says: ● There is a value, and it equals x ● There isn’t a value at all ● Only

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Optionals ● The concept of optionals doesn’t exist in C or Objective-C. The nearest thing in Objective-C is the ability to return nil ● However, this only works for objects - it doesn’t work for structures, basic C types, or enumeration values. Requires NSNotFound or something. ● Optionals in Swift work for everything

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Optionals var vaders: Int? = forceAwakensCharacters[“vader”] if(vaders == nil) { // do something } else { let count: Int = vaders! } if(vadersPhones) { let count: Int = vaders! }

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Optionals let cast = ["luke": 1, "wookie": 2] var vader : Int? = cast["vader"] if let vader = cast["vader"] { // Optional Binding } guard let vader = cast["vader"] else { break } var vader2: Int = cast["vader"]!

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Optionals Note: Trying to use ! to access a non-existent optional value triggers a runtime error. Always make sure that an optional contains a non-nil value before using ! to force-unwrap its value.

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If statements if myVar { print(“myVar, hurray!”) } else if herVar { } if(myVar) { } // braces are required

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Tuples ● Tuples group multiple values into a single compound value ● The values within a tuple can be of any type and do not have to be of the same type as each other.

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Tuples let http404Error = (404, "Not Found") // (Int, String) let (statusCode, statusMessage) = http404Error print("The status code is \(statusCode)") // prints "The status code is 404" print("The status message is \(statusMessage)") // prints "The status message is Not Found”

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Tuples let http200Status = (statusCode: 200, description: "OK") print("The status code is \(http200Status.statusCode)") // prints "The status code is 200" print("The status message is \(http200Status.description)") // prints "The status message is OK

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Tuples Pro Tip: Share data structure without sharing code with tuples

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Switch statements switch phoneCount { case 1: print(“One phone”) case 2,3,4: print(“More phones”) default: break } switch phoneCount { case [0, 1, 2]: print(“One phone”) case 3...6: print(“More phones”) default: break }

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Switch staments // There’s more! switch sender { case myTextField: print(“Text”) case myButton: print(“Button”) default: break }

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Functions func helloWorld { print(“Hello world”) } helloWorld() // prints ‘Hello World’

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Functions func helloWorld(name: String = “John”) { print(“Hello world \(name)”); } helloWorld() // prints ‘Hello World John’

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Functions func helloWorld(name: String = “John”) -> String { return “Hello world \(name)”; } let a: String = helloWorld()

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Closures ● Closures are self-contained blocks of functionality that can be passed around and used in your code. ● Closures in Swift are similar to blocks in C and Objective-C and to lambdas in other programming languages.

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Closures Closure expression syntax has the following general form: { (parameters) -> return type in statements }

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Closures let helloSayer: () -> () in { print(“Hello World”) } func doTask(task: () -> ()) { } doTask(helloSayer) doTask { print(“Hello”) }

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Classes - Swift has no universal base class - No #import “Bla.h” - Type inference - ARC

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Properties in Classes class Animal { // methods // properties // initializers } class Cat : Animal { var ears = 2 // property }

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Properties in Classes class Cat { var description: String { get { return “Cat Description” } set { } } } let someCat = Cat()

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Initializers & Overriding class Aegean : Cat { var ears init() { super.init() ears = 3 } override var someFunction: String { get { return “Cat Function” } }

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Property Observers class Cat { init() { mouth = “Big” } var mouth : String { willSet { // old value available here } didSet { // new value available here } }

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Methods class Aegean : Cat { func jump(amount: Int) { for int i = 0; i < amount; i++ { print(“jump”) } } }

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Error handling You use error handling to respond to error conditions your program may encounter during execution ● Determine the underlying cause of failure unlike optionals which only communicate the presence of a failure

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Error handling func canThrowAnError() throws { // this function may or may not throw an error } do { try canThrowAnError() // no error was thrown } catch { // an error was thrown }

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Getting started https://swift.org/getting-started/ Ray Tutorial OSX & Linux support No Cocoa for Linux ( ͡° ͜ʖ ͡°)

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Getting started Interesting cocoa free repos Epoch // HTTP server for Swift 2.2 on Linux Coolie // Coolie helps you to create models (& their constructors) from JSON file Style guide

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Ευχαριστούμε :) Dimitri James Tsiflitzis nimber, taxibeat, stonesoup, peopleperhour @sprimp github.com/tsif