Swift Cheat Sheet

Swift's some quick look-up tables, reproduced, but paste the code when the line is a problem, this How to solve?

Do not like the format can see the original: http://codeinswift.com/swift-cheat-sheet/

Basics

println ("Hello, World") var myvariable =//variable (can ' t is nil) letπ= 3.1415926//constant Let (x, y) = (10, 20)  x = ten, y = 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/Do 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&nbSp;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" VA R 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 is 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&Nbsp;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 is 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&NBSP, 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,&nbsp, ...)  rather than name numbers = [2, 5, 1]numbers.map { 3 *  $0 } // [6, 15, 3]

Classes

All methods and properties of a class is 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 Propertyvar Perimeter:int {get {return 4 * sidelength}set {sidelength = Newvalue/4}}init (si  Delength:int) {self.sidelength = Sidelengthsuper.init ()}func shrink () {if sidelength > 0 {--sidelength}}override func Getarea (), Int {return sidelength * sidelength}

} var mysquare = Square (sidelength:5) print (Mysquare.getarea ())//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) St EPS to ' Totalsteps ')}}} var stepcounter = Stepcounter () Stepcounter.totalsteps = +//About to set Totalsteps to 1 XX \ Added steps to ' totalsteps ' stepcounter.totalsteps = 145//About to set Totalsteps to 145 \ r Added ' Totalsteps '

If you don ' t need a custom getter and setter, but still want to run code//before an after getting or setting a proper Ty, you can use Willset and Didset

Enums

Enums can optionally is of a specific type or on their own. They can contain methods like classes.

Enum Suit {case spades, Hearts, Diamonds, Clubsfunc 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 Func Tionality.

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 has 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 the write flexible, reusable functions and types that can work with any type.

Generic function, which swaps the values. Func swaptwovalues<t> (inout a:t, inout b:t) {let Temporarya = AA = BB = 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 in the types with generic functions and generic types. use where after thetype 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 of the Unicode character (including emoji) as variable names or in Strings.

which, in Xcode looks like

Swift Cheat Sheet