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-rw-r--r--swift.html.markdown217
1 files changed, 156 insertions, 61 deletions
diff --git a/swift.html.markdown b/swift.html.markdown
index 509c9d2f..e921e7ea 100644
--- a/swift.html.markdown
+++ b/swift.html.markdown
@@ -3,8 +3,10 @@ language: swift
contributors:
- ["Grant Timmerman", "http://github.com/grant"]
- ["Christopher Bess", "http://github.com/cbess"]
- - ["Joey Huang", "http://github.com/kamidox"]
+ - ["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
---
@@ -12,7 +14,7 @@ Swift is a programming language for iOS and OS X development created by Apple. D
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/RoadMapiOS/index.html), which has a complete tutorial on Swift.
+See also Apple's [getting started guide](https://developer.apple.com/library/prerelease/ios/referencelibrary/GettingStarted/DevelopiOSAppsSwift/), which has a complete tutorial on Swift.
```swift
// import a module
@@ -24,12 +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
@@ -43,7 +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
@@ -57,13 +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 allows you to store a `Some` or
- `None` value.
+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)
@@ -74,16 +78,24 @@ if someOptionalString != nil {
if someOptionalString!.hasPrefix("opt") {
print("has the prefix")
}
-
+
let empty = someOptionalString?.isEmpty
}
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.
+*/
+
// 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 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") {
@@ -93,13 +105,13 @@ if let someOptionalStringConstant = someOptionalString {
// 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)
+// 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
*/
@@ -110,8 +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
@@ -120,6 +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
@@ -131,12 +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 {
@@ -166,8 +188,8 @@ while i < 1000 {
i *= 2
}
-// do-while loop
-do {
+// repeat-while loop
+repeat {
print("hello")
} while 1 == 2
@@ -186,7 +208,6 @@ default: // required (in order to cover all possible input)
let vegetableComment = "Everything tastes good in soup."
}
-
//
// MARK: Functions
//
@@ -194,28 +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) {
@@ -228,11 +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
@@ -253,7 +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
@@ -281,24 +324,18 @@ 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 capabilites
+// Structures and classes have very similar capabilities
struct NamesTable {
- let names = [String]()
-
+ let names: [String]
+
// Custom subscript
subscript(index: Int) -> String {
return names[index]
@@ -311,6 +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
//
@@ -319,7 +394,7 @@ print("Name is \(name)") // Name is Them
public class Shape {
public func getArea() -> Int {
- return 0;
+ return 0
}
}
@@ -329,7 +404,7 @@ public class Shape {
internal class Rect: Shape {
var sideLength: Int = 1
-
+
// Custom getter and setter property
private var perimeter: Int {
get {
@@ -340,11 +415,16 @@ internal class Rect: Shape {
sideLength = newValue / 4
}
}
-
+
+ // 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)
-
+
// 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`
@@ -354,19 +434,19 @@ internal class Rect: Shape {
print(someIdentifier)
}
}
-
+
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
}
@@ -398,13 +478,13 @@ class Circle: Shape {
override func getArea() -> Int {
return 3 * radius * radius
}
-
+
// Place a question mark postfix after `init` is an optional init
// which can return nil
init?(radius: Int) {
self.radius = radius
super.init()
-
+
if radius <= 0 {
return nil
}
@@ -445,9 +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)")
@@ -458,7 +539,7 @@ enum Furniture {
case Desk(height: Int)
// Associate with String and Int
case Chair(String, Int)
-
+
func description() -> String {
switch self {
case .Desk(let height):
@@ -491,22 +572,22 @@ 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
}
class MyShape: Rect {
var delegate: TransformShape?
-
+
func grow() {
sideLength += 2
// 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?()
}
}
}
@@ -518,8 +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)"
}
@@ -532,7 +613,7 @@ extension Int {
var customProperty: String {
return "This is \(self)"
}
-
+
func multiplyBy(num: Int) -> Int {
return num * self
}
@@ -544,8 +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
}
@@ -574,4 +655,18 @@ print(mySquare.sideLength) // 4
// change side length using custom !!! operator, increases size by 3
!!!mySquare
print(mySquare.sideLength) // 12
+
+// Operators can also be generics
+infix operator <-> {}
+func <-><T: Equatable> (inout a: T, inout b: T) {
+ let c = a
+ a = b
+ b = c
+}
+
+var foo: Float = 10
+var bar: Float = 20
+
+foo <-> bar
+print("foo is \(foo), bar is \(bar)") // "foo is 20.0, bar is 10.0"
```