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Swift Cheat Sheet
swift的一些速查表，转载过来的，但是粘贴代码的时候换行都出问题了，这个该怎么解决？
不喜欢格式的可以看原文：http://codeinswift.com/swift-cheat-sheet/
Basics
println("Hello, world")
var myVariable = 42 // variable (can‘t be nil)
let π = 3.1415926 // constant
let (x, y) = (10, 20) // x = 10, y = 20
let explicitDouble: Double = 1_000.000_1 // 1,000.0001
let label = "some text " + String(myVariable) // Casting
let piText = "Pi = \(π)" // String interpolation
var optionalString: String? = "optional" // Can be nil
optionalString = nil
/* Did you know /* you can nest multiline comments */ ? */
Arrays
// Array var shoppingList = ["catfish", "water", "lemons"]
shoppingList[1] = "bottle of water" // update shoppingList.count // size of array (3) shoppingList.append("eggs")
shoppingList += "Milk" // Array slicing var fibList = [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 5]
fibList[4..6] // [3, 5]. Note: the end range value is exclusive fibList[0..fibList.endIndex] // all except last item // Subscripting returns the Slice type, instead of the Array type. // You may need to cast it to Array in order to satisfy the type checker Array(fibList[0..4]) // Variants of creating an array. All three are equivalent. var emptyArray1 = String[]() var emptyArray2: String[] = [] var emptyArray3: String[] = String[]()
Dictionaries
// Dictionary var occupations = [ "Malcolm": "Captain", "kaylee": "Mechanic" ] occupations["Jayne"] = "Public Relations" var emptyDictionary = Dictionary<String, Float>()
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!")
}
} // for loop (dictionary) var dict = [ "name": "Steve Jobs", "title": "CEO", "company": "Apple" ] for (key, value) in dict {
println("\(key): \(value)")
} // for loop (range) for i in -1...1 { // [-1, 0, 1] println(i)
} // use .. to exclude the last number // for loop (ignoring the current value of the range on each iteration of the loop) for _ in 1...3 { // Do something three times. } // while loop var i = 1 while i < 1000 {
i *= 2 } // do-while loop do {
println("hello")
} while 1 == 2 // Switch let vegetable = "red pepper" switch vegetable { case "celery": 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)?" default: // required (in order to cover all possible input) let vegetableComment = "Everything tastes good in soup." } // Switch to validate plist content let city:Dictionary<String, AnyObject> = [ "name" : "Qingdao", "population" : 2_721_000, "abbr" : "QD" ] switch (city["name"], city["population"], city["abbr"]) { case (.Some(let cityName as NSString),
.Some(let pop as NSNumber),
.Some(let abbr as NSString))
where abbr.length == 2:
println("City Name: \(cityName) | Abbr.:\(abbr) Population: \(pop)") default:
println("Not a valid city")
}
Functions
Functions are a first-class type, meaning they can be nested in functions and can be passed around
// Function that returns a String func greet(name: String, day: String) -> String { return "Hello \(name), today is \(day)." }
greet("Bob", "Tuesday") // call the greet function // Function that returns multiple items in a tuple func getGasPrices() -> (Double, Double, Double) { return (3.59, 3.69, 3.79)
} // Function that takes variable number of arguments, collecting them into an array func setup(numbers: Int...) { // do something }
setup(5, 16, 38) // call the setup function with array of inputs // Nested functions can organize code that is long or complex func printWelcomeMessage() -> String { var y = "Hello," func add() {
y += " world" }
add() return y
}
printWelcomeMessage() // Hello world // Passing and returning functions func makeIncrementer() -> (Int -> Int) {
func addOne(number: Int) -> Int { return 1 + number
} return addOne
} var increment = makeIncrementer()
increment(7)
Closures
Functions are special case closures ({})
// Closure example. // `->` separates the arguments and return type // `in` separates the closure header from the closure body var numbers = [1, 2, 3, 4, 5]
numbers.map({
(number: Int) -> Int in let result = 3 * number return result
}) // When the type is known, like above, we can do this numbers = [1, 2, 6]
numbers = numbers.map({ number in 3 * number })
println(numbers) // [3, 6, 18] // When a closure is the last argument, you can place it after the ) // When a closure is the only argument, you can omit the () entirely // You can also refer to closure arguments by position ($0, $1, ...) rather than name numbers = [2, 5, 1]
numbers.map { 3 * $0 } // [6, 15, 3]
Classes
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
“`js // A parent class of Square class Shape { init() { }
func getArea() -> Int {
return 0;
}
}
// A simple class Square extends Shape class Square: Shape { var sideLength: Int
// Custom getter and setter property
var perimeter: Int {
get {
return 4 * sideLength
}
set {
sideLength = newValue / 4
}
}
init(sideLength: Int) {
self.sideLength = sideLength
super.init()
}
func shrink() {
if sideLength > 0 {
--sideLength
}
}
override func getArea() -> Int {
return sideLength * sideLength
}
} var mySquare = Square(sideLength: 5) print(mySquare.getArea()) // 25 mySquare.shrink() print(mySquare.sideLength) // 4
// Access the Square class object, // equivalent to [Square class] in Objective-C. Square.self
//example for ‘willSet’ and ‘didSet’ class StepCounter { var totalSteps: Int = 0 { willSet(newTotalSteps) { println(“About to set totalSteps to (newTotalSteps)”) } didSet { if totalSteps > oldValue { println(“Added (totalSteps – oldValue) steps to ‘totalSteps‘”) } } } } var stepCounter = StepCounter() stepCounter.totalSteps = 100 // About to set totalSteps to 100 \n Added 100 steps to ‘totalSteps’ stepCounter.totalSteps = 145 // About to set totalSteps to 145 \n Added 45 steps to ‘totalSteps’
// If you don’t need a custom getter and setter, but still want to run code // before an after getting or setting a property, you can use willSet and didSet
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 "?" }
}
}
Protocols
A protocol defines a blueprint of methods, properties, and other requirements that suit a particular task or piece of functionality.
protocol SomeProtocol { // protocol definition goes here }
Extensions
Add extra functionality to an already created type
// adds the methods first and rest to the array type extension Array {
func first () -> Any? { return self[0]
}
func rest () -> Array { if self.count >= 1 { return Array(self[1..self.endIndex])
} else { return []
}
}
}
Operator Overloading
You can overwrite existing operators or define new operators for existing or custom types.
// Overwrite existing types @infix func + (a: Int, b: Int) -> Int { return a - b
} var x = 5 + 4 // x is 1
You can’t overwrite the = operator
Add operators for new types
struct Vector2D { var x = 0.0, y = 0.0 }
@infix func + (left: Vector2D, right: Vector2D) -> Vector2D { return Vector2D(x: left.x + right.x, y: left.y + right.y)
}
Operators can be prefix, infix, or postfix.
You have to add @assignment if you wish to define compound assignment operators like +=, ++ or -=
@assignment func += (inout left: Vector2D, right: Vector2D) {
left = left + right
}
Operator overloading is limited to the following symbols: / = – + * % < > ! & | ^ . ~
Generics
Generic code enables you to write flexible, reusable functions and types that can work with any type.
// Generic function, which swaps two any values. func swapTwoValues<T>(inout a: T, inout b: T) { let temporaryA = a
a = b
b = temporaryA
}
// Generic collection type called `Stack`. struct Stack<T> { var elements = T[]()
mutating func push(element: T) {
elements.append(element)
}
mutating func pop() -> T { return elements.removeLast()
}
}
We can use certain type constraints on the types with generic functions and generic types. Use whereafter the type name to specify a list of requirements.
// Generic function, which checks that the sequence contains a specified value. func containsValue<
T where T: Sequence, T.GeneratorType.Element: Equatable>
(sequence: T, valueToFind: T.GeneratorType.Element) -> Bool { for value in sequence { if value == valueToFind { return true }
} return false }
In the simple cases, you can omit where and simply write the protocol or class name after a colon. Writing <T: Sequence> is the same as writing <T where T: Sequence>.
Emoji/Unicode support
You can use any unicode character (including emoji) as variable names or in Strings.
Which, in Xcode looks like 
Swift Cheat Sheet