diff options
Diffstat (limited to 'swift.html.markdown')
| -rw-r--r-- | swift.html.markdown | 167 |
1 files changed, 120 insertions, 47 deletions
diff --git a/swift.html.markdown b/swift.html.markdown index f451288d..e921e7ea 100644 --- a/swift.html.markdown +++ b/swift.html.markdown @@ -6,6 +6,7 @@ contributors: - ["Joey Huang", "http://github.com/kamidox"] - ["Anthony Nguyen", "http://github.com/anthonyn60"] - ["Clayton Walker", "https://github.com/cwalk"] + - ["Fernando Valverde", "http://visualcosita.xyz"] filename: learnswift.swift --- @@ -25,12 +26,13 @@ import UIKit // Xcode supports landmarks to annotate your code and lists them in the jump bar // MARK: Section mark +// MARK: - Section mark with a separator line // TODO: Do something soon // FIXME: Fix this code // In Swift 2, println and print were combined into one print method. Print automatically appends a new line. print("Hello, world") // println is now print -print("Hello, world", appendNewLine: false) // printing without appending a newline +print("Hello, world", terminator: "") // printing without appending a newline // variables (var) value can change after being set // constants (let) value can NOT be changed after being set @@ -44,7 +46,7 @@ let `class` = "keyword" // backticks allow keywords to be used as variable names let explicitDouble: Double = 70 let intValue = 0007 // 7 let largeIntValue = 77_000 // 77000 -let label = "some text " + String(myVariable) // Casting +let label = "some text " + String(myVariable) // String construction let piText = "Pi = \(π), Pi 2 = \(π * 2)" // String interpolation // Build Specific values @@ -58,14 +60,14 @@ let piText = "Pi = \(π), Pi 2 = \(π * 2)" // String interpolation print("Build value: \(buildValue)") // Build value: 7 /* - Optionals are a Swift language feature that either contains a value, - or contains nil (no value) to indicate that a value is missing. - A question mark (?) after the type marks the value as optional. +Optionals are a Swift language feature that either contains a value, +or contains nil (no value) to indicate that a value is missing. +A question mark (?) after the type marks the value as optional. - Because Swift requires every property to have a value, even nil must be - explicitly stored as an Optional 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. +Optional<T> is an enum. */ var someOptionalString: String? = "optional" // Can be nil // same as above, but ? is a postfix operator (syntax candy) @@ -82,9 +84,9 @@ if someOptionalString != nil { someOptionalString = nil /* - 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. +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. */ // implicitly unwrapped optional @@ -92,6 +94,8 @@ 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 structure - +// If let is a special structure in Swift that allows you to check if an Optional rhs holds a value, and in case it does - unwraps and assigns it to the lhs. if let someOptionalStringConstant = someOptionalString { // has `Some` value, non-nil if !someOptionalStringConstant.hasPrefix("ok") { @@ -118,8 +122,8 @@ anyObjectVar = "Changed value to a string, not good practice, but possible." // /* - 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 and Dictionary types are structs. So `let` and `var` also indicate +that they are mutable (var) or immutable (let) when declaring these types. */ // Array @@ -128,6 +132,7 @@ shoppingList[1] = "bottle of water" let emptyArray = [String]() // let == immutable let emptyArray2 = Array<String>() // same as above var emptyMutableArray = [String]() // var == mutable +var explicitEmptyMutableStringArray: [String] = [] // same as above // Dictionary @@ -139,12 +144,21 @@ occupations["Jayne"] = "Public Relations" let emptyDictionary = [String: Float]() // let == immutable let emptyDictionary2 = Dictionary<String, Float>() // same as above var emptyMutableDictionary = [String: Float]() // var == mutable +var explicitEmptyMutableDictionary: [String: Float] = [:] // same as above // // MARK: Control Flow // +// Condition statements support "where" clauses, which can be used +// to help provide conditions on optional values. +// Both the assignment and the "where" clause must pass. +let someNumber = Optional<Int>(7) +if let num = someNumber where num > 3 { + print("num is greater than 3") +} + // for loop (array) let myArray = [1, 1, 2, 3, 5] for value in myArray { @@ -174,8 +188,8 @@ while i < 1000 { i *= 2 } -// do-while loop -do { +// repeat-while loop +repeat { print("hello") } while 1 == 2 @@ -194,7 +208,6 @@ default: // required (in order to cover all possible input) let vegetableComment = "Everything tastes good in soup." } - // // MARK: Functions // @@ -202,28 +215,28 @@ default: // required (in order to cover all possible input) // Functions are a first-class type, meaning they can be nested // in functions and can be passed around -// Function with Swift header docs (format as reStructedText) +// Function with Swift header docs (format as Swift-modified Markdown syntax) /** - A greet operation +A greet operation - - A bullet in docs - - Another bullet in the docs +- 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. +- Parameter name : A name +- Parameter 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)." } -greet("Bob", "Tuesday") +greet("Bob", day: "Tuesday") // similar to above except for the function parameter behaviors -func greet2(#requiredName: String, externalParamName localParamName: String) -> String { +func greet2(requiredName requiredName: String, externalParamName localParamName: String) -> String { return "Hello \(requiredName), the day is \(localParamName)" } -greet2(requiredName:"John", externalParamName: "Sunday") +greet2(requiredName: "John", externalParamName: "Sunday") // Function that returns multiple items in a tuple func getGasPrices() -> (Double, Double, Double) { @@ -236,11 +249,33 @@ let (_, price1, _) = pricesTuple // price1 == 3.69 print(price1 == pricesTuple.1) // true print("Gas price: \(price)") +// Labeled/named tuple params +func getGasPrices2() -> (lowestPrice: Double, highestPrice: Double, midPrice: Double) { + return (1.77, 37.70, 7.37) +} +let pricesTuple2 = getGasPrices2() +let price2 = pricesTuple2.lowestPrice +let (_, price3, _) = pricesTuple2 +print(pricesTuple2.highestPrice == pricesTuple2.1) // true +print("Highest gas price: \(pricesTuple2.highestPrice)") + +// guard statements +func testGuard() { + // guards provide early exits or breaks, placing the error handler code near the conditions. + // it places variables it declares in the same scope as the guard statement. + guard let aNumber = Optional<Int>(7) else { + return + } + + print("number is \(aNumber)") +} +testGuard() + // Variadic Args func setup(numbers: Int...) { // its an array - let number = numbers[0] - let argCount = numbers.count + let _ = numbers[0] + let _ = numbers.count } // Passing and returning functions @@ -261,7 +296,7 @@ func swapTwoInts(inout a: Int, inout b: Int) { } var someIntA = 7 var someIntB = 3 -swapTwoInts(&someIntA, &someIntB) +swapTwoInts(&someIntA, b: &someIntB) print(someIntB) // 7 @@ -289,23 +324,17 @@ numbers = numbers.map({ number in 3 * number }) print(numbers) // [3, 6, 18] // Trailing closure -numbers = sorted(numbers) { $0 > $1 } +numbers = numbers.sort { $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 capabilities struct NamesTable { - let names = [String]() + let names: [String] // Custom subscript subscript(index: Int) -> String { @@ -319,6 +348,44 @@ let name = namesTable[1] print("Name is \(name)") // Name is Them // +// MARK: Error Handling +// + +// The `ErrorType` protocol is used when throwing errors to catch +enum MyError: ErrorType { + case BadValue(msg: String) + case ReallyBadValue(msg: String) +} + +// functions marked with `throws` must be called using `try` +func fakeFetch(value: Int) throws -> String { + guard 7 == value else { + throw MyError.ReallyBadValue(msg: "Some really bad value") + } + + return "test" +} + +func testTryStuff() { + // assumes there will be no error thrown, otherwise a runtime exception is raised + let _ = try! fakeFetch(7) + + // if an error is thrown, then it proceeds, but if the value is nil + // it also wraps every return value in an optional, even if its already optional + let _ = try? fakeFetch(7) + + do { + // normal try operation that provides error handling via `catch` block + try fakeFetch(1) + } catch MyError.BadValue(let msg) { + print("Error message: \(msg)") + } catch { + // must be exhaustive + } +} +testTryStuff() + +// // MARK: Classes // @@ -327,7 +394,7 @@ print("Name is \(name)") // Name is Them public class Shape { public func getArea() -> Int { - return 0; + return 0 } } @@ -349,6 +416,11 @@ internal class Rect: Shape { } } + // Computed properties must be declared as `var`, you know, cause' they can change + var smallestSideLength: Int { + return self.sideLength - 1 + } + // Lazily load a property // subShape remains nil (uninitialized) until getter called lazy var subShape = Rect(sideLength: 4) @@ -453,9 +525,10 @@ enum Suit { // when the variable is explicitly declared var suitValue: Suit = .Hearts -// Non-Integer enums require direct raw value assignments +// String enums can have direct raw value assignments +// or their raw values will be derived from the Enum field enum BookName: String { - case John = "John" + case John case Luke = "Luke" } print("Name: \(BookName.John.rawValue)") @@ -499,7 +572,7 @@ protocol ShapeGenerator { // Protocols declared with @objc allow optional functions, // which allow you to check for conformance @objc protocol TransformShape { - optional func reshaped() + optional func reshape() optional func canReshape() -> Bool } @@ -512,9 +585,9 @@ class MyShape: Rect { // Place a question mark after an optional property, method, or // subscript to gracefully ignore a nil value and return nil // instead of throwing a runtime error ("optional chaining"). - if let allow = self.delegate?.canReshape?() { + if let reshape = self.delegate?.canReshape?() where reshape { // test for delegate then for method - self.delegate?.reshaped?() + self.delegate?.reshape?() } } } @@ -526,8 +599,8 @@ class MyShape: Rect { // `extension`s: Add extra functionality to an already existing type -// Square now "conforms" to the `Printable` protocol -extension Square: Printable { +// Square now "conforms" to the `CustomStringConvertible` protocol +extension Square: CustomStringConvertible { var description: String { return "Area: \(self.getArea()) - ID: \(self.identifier)" } @@ -552,8 +625,8 @@ print(14.multiplyBy(3)) // 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) { +func findIndex<T: Equatable>(array: [T], _ valueToFind: T) -> Int? { + for (index, value) in array.enumerate() { if value == valueToFind { return index } |