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Diffstat (limited to 'swift.html.markdown')
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diff --git a/swift.html.markdown b/swift.html.markdown index 6d98b067..0d1d2df4 100644 --- a/swift.html.markdown +++ b/swift.html.markdown @@ -2,130 +2,259 @@ language: swift contributors: - ["Grant Timmerman", "http://github.com/grant"] + - ["Christopher Bess", "http://github.com/cbess"] filename: learnswift.swift --- -Swift is a programming language for iOS and OS X development created by Apple. Designed to coexist with Objective-C and to be more resilient against erroneous code, Swift was introduced in 2014 at Apple's developer conference WWDC. It is built with the LLVM compiler included in Xcode 6 beta. +Swift is a programming language for iOS and OS X development created by Apple. Designed to coexist with Objective-C and to be more resilient against erroneous code, Swift was introduced in 2014 at Apple's developer conference WWDC. It is built with the LLVM compiler included in Xcode 6+. + +The official [Swift Programming Language](https://itunes.apple.com/us/book/swift-programming-language/id881256329) book from Apple is now available via iBooks. See also Apple's [getting started guide](https://developer.apple.com/library/prerelease/ios/referencelibrary/GettingStarted/LandingPage/index.html), which has a complete tutorial on Swift. -```js +```swift +// import a module +import UIKit + // -// Basics +// MARK: Basics // +// Xcode supports landmarks to annotate your code and lists them in the jump bar +// MARK: Section mark +// TODO: Do something soon +// FIXME: Fix this code + println("Hello, world") + +// variables (var) value can change after being set +// constants (let) value can NOT be changed after being set + var myVariable = 42 -let myConstant = 3.1415926 +let øπΩ = "value" // unicode variable names +let π = 3.1415926 +let convenience = "keyword" // contextual variable name +let weak = "keyword"; let override = "another keyword" // statements can be separated by a semi-colon +let `class` = "keyword" // backticks allow keywords to be used as variable names let explicitDouble: Double = 70 -let label = "some text " + String(myVariable) // Casting -let piText = "Pi = \(myConstant)" // String interpolation -var optionalString: String? = "optional" // Can be nil -optionalString = nil +let intValue = 0007 // 7 +let largeIntValue = 77_000 // 77000 +let label = "some text " + String(myVariable) // Casting +let piText = "Pi = \(π), Pi 2 = \(π * 2)" // String interpolation + +// Build Specific values +// uses -D build configuration +#if false + println("Not printed") + let buildValue = 3 +#else + let buildValue = 7 +#endif +println("Build value: \(buildValue)") // Build value: 7 + +/* + Optionals are a Swift language feature that allows you to store a `Some` or + `None` value. + + Because Swift requires every property to have a value, even nil must be + explicitly stored as an Optional value. + + Optional<T> is an enum. +*/ +var someOptionalString: String? = "optional" // Can be nil +// same as above, but ? is a postfix operator (syntax candy) +var someOptionalString2: Optional<String> = "optional" + +if someOptionalString != nil { + // I am not nil + if someOptionalString!.hasPrefix("opt") { + println("has the prefix") + } + + let empty = someOptionalString?.isEmpty +} +someOptionalString = nil + +// implicitly unwrapped optional +var unwrappedString: String! = "Value is expected." +// same as above, but ! is a postfix operator (more syntax candy) +var unwrappedString2: ImplicitlyUnwrappedOptional<String> = "Value is expected." + +if let someOptionalStringConstant = someOptionalString { + // has `Some` value, non-nil + if !someOptionalStringConstant.hasPrefix("ok") { + // does not have the prefix + } +} +// Swift has support for storing a value of any type. +// AnyObject == id +// Unlike Objective-C `id`, AnyObject works with any value (Class, Int, struct, etc) +var anyObjectVar: AnyObject = 7 +anyObjectVar = "Changed value to a string, not good practice, but possible." + +/* + Comment here + + /* + Nested comments are also supported + */ +*/ // -// Arrays and Dictionaries +// MARK: Collections // +/* + Array and Dictionary types are structs. So `let` and `var` also indicate + that they are mutable (var) or immutable (let) when declaring these types. +*/ + // Array var shoppingList = ["catfish", "water", "lemons"] shoppingList[1] = "bottle of water" -let emptyArray = [String]() +let emptyArray = [String]() // let == immutable +let emptyArray2 = Array<String>() // same as above +var emptyMutableArray = [String]() // var == mutable + // Dictionary var occupations = [ - "Malcolm": "Captain", - "kaylee": "Mechanic" + "Malcolm": "Captain", + "kaylee": "Mechanic" ] occupations["Jayne"] = "Public Relations" -let emptyDictionary = [String: Float]() +let emptyDictionary = [String: Float]() // let == immutable +let emptyDictionary2 = Dictionary<String, Float>() // same as above +var emptyMutableDictionary = [String: Float]() // var == mutable // -// Control Flow +// MARK: Control Flow // // for loop (array) let myArray = [1, 1, 2, 3, 5] for value in myArray { - if value == 1 { - println("One!") - } else { - println("Not one!") - } + if value == 1 { + println("One!") + } else { + println("Not one!") + } } // for loop (dictionary) +var dict = ["one": 1, "two": 2] for (key, value) in dict { - println("\(key): \(value)") + println("\(key): \(value)") } // for loop (range) -for i in -1...1 { // [-1, 0, 1] - println(i) +for i in -1...shoppingList.count { + println(i) } +shoppingList[1...2] = ["steak", "peacons"] // use ..< to exclude the last number // while loop var i = 1 while i < 1000 { - i *= 2 + i *= 2 } // do-while loop do { - println("hello") + println("hello") } while 1 == 2 // Switch +// Very powerful, think `if` statements with syntax candy +// They support String, object instances, and primitives (Int, Double, etc) let vegetable = "red pepper" switch vegetable { case "celery": - let vegetableComment = "Add some raisins and make ants on a log." + let vegetableComment = "Add some raisins and make ants on a log." case "cucumber", "watercress": - let vegetableComment = "That would make a good tea sandwich." -case let x where x.hasSuffix("pepper"): - let vegetableComment = "Is it a spicy \(x)?" + let vegetableComment = "That would make a good tea sandwich." +case let localScopeValue where localScopeValue.hasSuffix("pepper"): + let vegetableComment = "Is it a spicy \(localScopeValue)?" default: // required (in order to cover all possible input) - let vegetableComment = "Everything tastes good in soup." + let vegetableComment = "Everything tastes good in soup." } // -// Functions +// MARK: Functions // // Functions are a first-class type, meaning they can be nested // in functions and can be passed around -// Function +// Function with Swift header docs (format as reStructedText) + +/** + A greet operation + + - A bullet in docs + - Another bullet in the docs + + :param: name A name + :param: day A day + :returns: A string containing the name and day value. +*/ func greet(name: String, day: String) -> String { - return "Hello \(name), today is \(day)." + return "Hello \(name), today is \(day)." } greet("Bob", "Tuesday") +// similar to above except for the function parameter behaviors +func greet2(#requiredName: String, externalParamName localParamName: String) -> String { + return "Hello \(requiredName), the day is \(localParamName)" +} +greet2(requiredName:"John", externalParamName: "Sunday") + // Function that returns multiple items in a tuple func getGasPrices() -> (Double, Double, Double) { - return (3.59, 3.69, 3.79) + return (3.59, 3.69, 3.79) +} +let pricesTuple = getGasPrices() +let price = pricesTuple.2 // 3.79 +// Ignore Tuple (or other) values by using _ (underscore) +let (_, price1, _) = pricesTuple // price1 == 3.69 +println(price1 == pricesTuple.1) // true +println("Gas price: \(price)") + +// Variadic Args +func setup(numbers: Int...) { + // its an array + let number = numbers[0] + let argCount = numbers.count } - -// Args -func setup(numbers: Int...) {} // Passing and returning functions func makeIncrementer() -> (Int -> Int) { - func addOne(number: Int) -> Int { - return 1 + number - } - return addOne + func addOne(number: Int) -> Int { + return 1 + number + } + return addOne } var increment = makeIncrementer() increment(7) +// pass by ref +func swapTwoInts(inout a: Int, inout b: Int) { + let tempA = a + a = b + b = tempA +} +var someIntA = 7 +var someIntB = 3 +swapTwoInts(&someIntA, &someIntB) +println(someIntB) // 7 + // -// Closures +// MARK: Closures // var numbers = [1, 2, 6] @@ -135,93 +264,256 @@ var numbers = [1, 2, 6] // `->` separates the arguments and return type // `in` separates the closure header from the closure body numbers.map({ - (number: Int) -> Int in - let result = 3 * number - return result - }) + (number: Int) -> Int in + let result = 3 * number + return result +}) // When the type is known, like above, we can do this numbers = numbers.map({ number in 3 * number }) -//Or even this +// Or even this //numbers = numbers.map({ $0 * 3 }) print(numbers) // [3, 6, 18] +// Trailing closure +numbers = sorted(numbers) { $0 > $1 } + +print(numbers) // [18, 6, 3] + +// Super shorthand, since the < operator infers the types + +numbers = sorted(numbers, < ) + +print(numbers) // [3, 6, 18] + +// +// MARK: Structures +// + +// Structures and classes have very similar capabilites +struct NamesTable { + let names = [String]() + + // Custom subscript + subscript(index: Int) -> String { + return names[index] + } +} + +// Structures have an auto-generated (implicit) designated initializer +let namesTable = NamesTable(names: ["Me", "Them"]) +let name = namesTable[1] +println("Name is \(name)") // Name is Them // -// Classes +// MARK: Classes // +// Classes, structures and its members have three levels of access control +// They are: internal (default), public, private + +public class Shape { + public func getArea() -> Int { + return 0; + } +} + // All methods and properties of a class are public. // If you just need to store data in a // structured object, you should use a `struct` -// A simple class `Square` extends `Shape` -class Square: Shape { - var sideLength: Int = 1 - - // Custom getter and setter property - var perimeter: Int { - get { - return 4 * sideLength +internal class Rect: Shape { + var sideLength: Int = 1 + + // Custom getter and setter property + private var perimeter: Int { + get { + return 4 * sideLength + } + set { + // `newValue` is an implicit variable available to setters + sideLength = newValue / 4 + } } - set { - sideLength = newValue / 4 + + // Lazily load a property + // subShape remains nil (uninitialized) until getter called + lazy var subShape = Rect(sideLength: 4) + + // If you don't need a custom getter and setter, + // but still want to run code before and after getting or setting + // a property, you can use `willSet` and `didSet` + var identifier: String = "defaultID" { + // the `willSet` arg will be the variable name for the new value + willSet(someIdentifier) { + print(someIdentifier) + } } - } - - init(sideLength: Int) { - super.init() - self.sideLength = sideLength - } - - func shrink() { - if sideLength > 0 { - --sideLength + + init(sideLength: Int) { + self.sideLength = sideLength + // always super.init last when init custom properties + super.init() + } + + func shrink() { + if sideLength > 0 { + --sideLength + } + } + + override func getArea() -> Int { + return sideLength * sideLength } - } +} - override func getArea() -> Int { - return sideLength * sideLength - } +// A simple class `Square` extends `Rect` +class Square: Rect { + convenience init() { + self.init(sideLength: 5) + } } -var mySquare = new Square(sideLength: 5) + +var mySquare = Square() print(mySquare.getArea()) // 25 mySquare.shrink() print(mySquare.sideLength) // 4 -// If you don't need a custom getter and setter, -// but still want to run code before and after getting or setting -// a property, you can use `willSet` and `didSet` +// cast instance +let aShape = mySquare as Shape + +// compare instances, not the same as == which compares objects (equal to) +if mySquare === mySquare { + println("Yep, it's mySquare") +} // -// Enums +// MARK: Enums // // Enums can optionally be of a specific type or on their own. // They can contain methods like classes. enum Suit { - case Spades, Hearts, Diamonds, Clubs - func getIcon() -> String { - switch self { - case .Spades: return "♤" - case .Hearts: return "♡" - case .Diamonds: return "♢" - case .Clubs: return "♧" + case Spades, Hearts, Diamonds, Clubs + func getIcon() -> String { + switch self { + case .Spades: return "♤" + case .Hearts: return "♡" + case .Diamonds: return "♢" + case .Clubs: return "♧" + } + } +} + +// Enum values allow short hand syntax, no need to type the enum type +// when the variable is explicitly declared +var suitValue: Suit = .Hearts + +// Non-Integer enums require direct raw value assignments +enum BookName: String { + case John = "John" + case Luke = "Luke" +} +println("Name: \(BookName.John.rawValue)") + + +// +// MARK: Protocols +// + +// `protocol`s can require that conforming types have specific +// instance properties, instance methods, type methods, +// operators, and subscripts. + +protocol ShapeGenerator { + var enabled: Bool { get set } + func buildShape() -> Shape +} + +// Protocols declared with @objc allow optional functions, +// which allow you to check for conformance +@objc protocol TransformShape { + optional func reshaped() + optional func canReshape() -> Bool +} + +class MyShape: Rect { + var delegate: TransformShape? + + func grow() { + sideLength += 2 + + if let allow = self.delegate?.canReshape?() { + // test for delegate then for method + self.delegate?.reshaped?() + } } - } } // -// Other +// MARK: Other // -// `protocol`: Similar to Java interfaces. -// `extension`s: Add extra functionality to an already created type -// Generics: Similar to Java. Use the `where` keyword to specify the +// `extension`s: Add extra functionality to an already existing type + +// Square now "conforms" to the `Printable` protocol +extension Square: Printable { + var description: String { + return "Area: \(self.getArea()) - ID: \(self.identifier)" + } +} + +println("Square: \(mySquare)") + +// You can also extend built-in types +extension Int { + var customProperty: String { + return "This is \(self)" + } + + func multiplyBy(num: Int) -> Int { + return num * self + } +} + +println(7.customProperty) // "This is 7" +println(14.multiplyBy(2)) // 42 + +// Generics: Similar to Java and C#. Use the `where` keyword to specify the // requirements of the generics. +func findIndex<T: Equatable>(array: [T], valueToFind: T) -> Int? { + for (index, value) in enumerate(array) { + if value == valueToFind { + return index + } + } + return nil +} +let foundAtIndex = findIndex([1, 2, 3, 4], 3) +println(foundAtIndex == 2) // true + +// Operators: +// Custom operators can start with the characters: +// / = - + * % < > ! & | ^ . ~ +// or +// Unicode math, symbol, arrow, dingbat, and line/box drawing characters. +prefix operator !!! {} + +// A prefix operator that triples the side length when used +prefix func !!! (inout shape: Square) -> Square { + shape.sideLength *= 3 + return shape +} + +// current value +println(mySquare.sideLength) // 4 + +// change side length using custom !!! operator, increases size by 3 +!!!mySquare +println(mySquare.sideLength) // 12 ``` |