Swift 快速参考

本文是苹果Swift编程语言的备忘单和参考之南，以后会涵盖Swift的所有关键特性，包括Strings、Arrays、Dictionaries以及Flow Control。Swift是苹果在WWDC 2014上发布的适用于iOS和OS X平台应用的开发。（持续更新的内容，欢迎你来贴自己的备忘单）

Variables

var myInt = 1 
var myExplicitInt: Int = 1 // explicit type 
var x = 1, y = 2, z = 3 // declare multiple integers 
myExplicitInt = 2 // set to another integer value 

Constants

let myInt = 1 
myInt = 2 // compile-time error! 

Strings

var myString = "a" 
let myImmutableString = "c" 
myString += "b" // ab 
myString = myString + myImmutableString // abc 
myImmutableString += "d" // compile-time error! 
 
let count = 7 
let message = "There are \(count) days in a week" 

Logical Operators

var happy = true 
var sad = !happy // logical NOT, sad = false 
var everyoneHappy = happy && sad // logical AND, everyoneHappy = false 
var someoneHappy = happy || sad // logical OR, someoneHappy = true 

Printing

let name = "swift" 
println("Hello") 
println("My name is \(name)") 
print("See you ") 
print("later") 
/*  Hello 
    My name is swift 
    See you later */ 

Arrays

var colors = ["red", "blue"] 
var moreColors: String[] = ["orange", "purple"] // explicit type 
colors.append("green") // [red, blue, green] 
colors += "yellow" // [red, blue, green, yellow] 
colors += moreColors // [red, blue, green, yellow, orange, purple] 
 
var days = ["mon", "thu"] 
var firstDay = days[0] // mon 
days.insert("tue", atIndex: 1) // [mon, tue, thu] 
days[2] = "wed" // [mon, tue, wed] 
days.removeAtIndex(0) // [tue, wed]  

Dictionaries

var days = ["mon": "monday", "tue": "tuseday"] 
days["tue"] = "tuesday" // change the value for key "tue" 
days["wed"] = "wednesday" // add a new key/value pair 
 
var moreDays: Dictionary = ["thu": "thursday", "fri": "friday"] 
moreDays["thu"] = nil // remove thu from the dictionary 
moreDays.removeValueForKey("fri") // remove fri from the dictionary 
 

Conditionals

//IF STATEMENT 
let happy = true 
if happy { 
    println("We're Happy!") 
} else { 
    println("We're Sad :('") 
} 
// We're Happy! 
 
let speed = 28 
if speed <= 0 { 
    println("Stationary") 
} else if speed <= 30 { 
    println("Safe speed") 
} else { 
    println("Too fast!") 
} 
// Safe speed 
 
 
//SWITCH STATEMENT 
let n = 2 
switch n { 
case 1: 
    println("It's 1!") 
case 2...4: 
    println("It's between 2 and 4!") 
case 5, 6: 
    println("It's 5 or 6") 
default: 
    println("Its another number!") 
} 
// It's between 2 and 4! 

For Loops

for var index = 1; index < 3; ++index { 
    // loops with index taking values 1,2  
} 
for index in 1..3 { 
    // loops with index taking values 1,2 
} 
for index in 1...3 {  
    // loops with index taking values 1,2,3 
} 
 
let colors = ["red", "blue", "yellow"] 
for color in colors { 
    println("Color: \(color)") 
} 
// Color: red 
// Color: blue 
// Color: yellow  
 
let days = ["mon": "monday", "tue": "tuesday"] 
for (shortDay, longDay) in days { 
    println("\(shortDay) is short for \(longDay)") 
} 
// mon is short for monday 
// tue is short for tuesday 
 

While Loops

var count = 1 
while count < 3 { 
    println("count is \(count)") 
    ++count 
} 
// count is 1 
// count is 2 
 
count = 1 
while count < 1 { 
    println("count is \(count)") 
    ++count 
} 
// 
 
 
count = 1 
do { 
    println("count is \(count)") 
    ++count 
} while count < 3 
// count is 1 
// count is 2 
 
count = 1 
do { 
    println("count is \(count)") 
    ++count 
} while count < 1 
// count is 1 

另附上raywenderlich上Ray Wenderlich的备忘单。