class SomeClass {
 func someMethod() {
 if x == y {
  /* ... */
 } else if x == z {
  /* ... */
 } else {
  /* ... */
 }
 }
 /* ... */
}

let array = [1, 2, 3, 4, 5];

let value = 20 + (34 / 2) * 3
if 1 + 1 == 2 {
 //TODO
}
func pancake -> Pancake {
 /** do something **/
}

// Xcode针对跨多行函数声明缩进
func myFunctionWithManyParameters(parameterOne: String,
     parameterTwo: String,
     parameterThree: String) {
 // Xcode会自动缩进
 print("\(parameterOne) \(parameterTwo) \(parameterThree)")
}
// Xcode针对多行 if 语句的缩进
if myFirstVariable > (mySecondVariable + myThirdVariable)
 && myFourthVariable == .SomeEnumValue {
 // Xcode会自动缩进
 print("Hello, World!")
}

functionWithArguments(
 firstArgument: "Hello, I am a string",
 secondArgument: resultFromSomeFunction()
 thirdArgument: someOtherLocalVariable)

functionWithBunchOfArguments(
 someStringArgument: "hello I am a string",
 someArrayArgument: [
 "dadada daaaa daaaa dadada daaaa daaaa dadada daaaa daaaa",
 "string one is crazy - what is it thinking?"
 ],
 someDictionaryArgument: [
 "dictionary key 1": "some value 1, but also some more text here",
 "dictionary key 2": "some value 2"
 ],
 someClosure: { parameter1 in
 print(parameter1)
 })

// 推荐
let firstCondition = x == firstReallyReallyLongPredicateFunction()
let secondCondition = y == secondReallyReallyLongPredicateFunction()
let thirdCondition = z == thirdReallyReallyLongPredicateFunction()
if firstCondition && secondCondition && thirdCondition {
 // 你要干什么
}
// 不推荐
if x == firstReallyReallyLongPredicateFunction()
 && y == secondReallyReallyLongPredicateFunction()
 && z == thirdReallyReallyLongPredicateFunction() {
 // 你要干什么
}

// "HTML" 是变量名的开头, 需要全部小写 "html"
let htmlBodyContent: String = "<p>Hello, World!</p>"
// 推荐使用 ID 而不是 Id
let profileID: Int = 1
// 推荐使用 URLFinder 而不是 UrlFinder
class URLFinder {
 /* ... */
}

class ClassName {
 // 基元常量使用 k 作为前缀
 static let kSomeConstantHeight: CGFloat = 80.0
 // 非基元常量也是用 k 作为前缀
 static let kDeleteButtonColor = UIColor.redColor()
 // 对于单例不要使用k作为前缀
 static let sharedInstance = MyClassName()
 /* ... */
}

// 推荐
class RoundAnimatingButton: UIButton { /* ... */ }
// 不推荐
class CustomButton: UIButton { /* ... */ }

// 推荐
class RoundAnimatingButton: UIButton {
 let animationDuration: NSTimeInterval
 func startAnimating() {
 let firstSubview = subviews.first
 }
}
// 不推荐
class RoundAnimating: UIButton {
 let aniDur: NSTimeInterval
 func srtAnmating() {
 let v = subviews.first
 }
}

// 推荐
class ConnectionTableViewCell: UITableViewCell {
 let personImageView: UIImageView
 let animationDuration: NSTimeInterval
 // 作为属性名的firstName，很明显是字符串类型，所以不用在命名里不用包含String
 let firstName: String
 // 虽然不推荐, 这里用 Controller 代替 ViewController 也可以。
 let popupController: UIViewController
 let popupViewController: UIViewController
 // 如果需要使用UIViewController的子类，如TableViewController, CollectionViewController, SplitViewController, 等，需要在命名里标名类型。
 let popupTableViewController: UITableViewController
 // 当使用outlets时, 确保命名中标注类型。
 @IBOutlet weak var submitButton: UIButton!
 @IBOutlet weak var emailTextField: UITextField!
 @IBOutlet weak var nameLabel: UILabel!
}
// 不推荐
class ConnectionTableViewCell: UITableViewCell {
 // 这个不是 UIImage, 不应该以Image 为结尾命名。
 // 建议使用 personImageView
 let personImage: UIImageView
 // 这个不是String，应该命名为 textLabel
 let text: UILabel
 // animation 不能清晰表达出时间间隔
 // 建议使用 animationDuration 或 animationTimeInterval
 let animation: NSTimeInterval
 // transition 不能清晰表达出是String
 // 建议使用 transitionText 或 transitionString
 let transition: String
 // 这个是ViewController，不是View
 let popupView: UIViewController
 // 由于不建议使用缩写，这里建议使用 ViewController替换 VC
 let popupVC: UIViewController
 // 技术上讲这个变量是 UIViewController, 但应该表达出这个变量是TableViewController
 let popupViewController: UITableViewController
 // 为了保持一致性，建议把类型放到变量的结尾，而不是开始，如submitButton
 @IBOutlet weak var btnSubmit: UIButton!
 @IBOutlet weak var buttonSubmit: UIButton!
 // 在使用outlets 时，变量名内应包含类型名。
 // 这里建议使用 firstNameLabel
 @IBOutlet weak var firstName: UILabel!
}

// 推荐
let stringOfInts = [1, 2, 3].flatMap { String($0) }
// ["1", "2", "3"]
// 不推荐
var stringOfInts: [String] = []
for integer in [1, 2, 3] {
 stringOfInts.append(String(integer))
}

// 推荐
let evenNumbers = [4, 8, 15, 16, 23, 42].filter { $0 % 2 == 0 }
// [4, 8, 16, 42]
// 不推荐
var evenNumbers: [Int] = []
for integer in [4, 8, 15, 16, 23, 42] {
 if integer % 2 == 0 {
 evenNumbers(integer)
 }
}

func pirateName() -> (firstName: String, lastName: String) {
 return ("Guybrush", "Threepwood")
}
let name = pirateName()
let firstName = name.firstName
let lastName = name.lastName

functionWithClosure() { [weak self] (error) -> Void in
 // 方案 1
 self?.doSomething()
 // 或方案 2
 guard let strongSelf = self else {
 return
 }
 strongSelf.doSomething()
}

// 推荐
if x == y {
 /* ... */
}
// 不推荐
if (x == y) {
 /* ... */
}

// 推荐
imageView.setImageWithURL(url, type: .person)
// 不推荐
imageView.setImageWithURL(url, type: AsyncImageView.Type.person)

// 推荐
imageView.backgroundColor = UIColor.whiteColor()
// 不推荐
imageView.backgroundColor = .whiteColor()

if someBoolean {
 // 你想要什么
} else {
 // 你不想做什么
}
do {
 let fileContents = try readFile("filename.txt")
} catch {
 print(error)
}

// 推荐
private static let kMyPrivateNumber: Int
// 不推荐
static private let kMyPrivateNumber: Int

// 推荐
public class Pirate {
 /* ... */
}
// 不推荐
public
class Pirate {
 /* ... */
}

/**
 这个变量是private 名字
 - warning: 定义为 internal 而不是 private 为了 `@testable`.
 */
let pirateName = "LeChuck"

enum Problem {
 case attitude
 case hair
 case hunger(hungerLevel: Int)
}
func handleProblem(problem: Problem) {
 switch problem {
 case .attitude:
 print("At least I don't have a hair problem.")
 case .hair:
 print("Your barber didn't know when to stop.")
 case .hunger(let hungerLevel):
 print("The hunger level is \(hungerLevel).")
 }
}

func handleDigit(digit: Int) throws {
 case 0, 1, 2, 3, 4, 5, 6, 7, 8, 9:
  print("Yes, \(digit) is a digit!")
 default:
  throw Error(message: "The given number was not a digit.")
}

// 推荐
if nil != someOptional {
 // 你要做什么
}
// 不推荐
if let _ = someOptional {
 // 你要做什么
}

// 推荐
weak var parentViewController: UIViewController?
// 不推荐
weak var parentViewController: UIViewController!
unowned var parentViewController: UIViewController

guard let myVariable = myVariable else {
 return
}

var computedProperty: String {
 if someBool {
  return "I'm a mighty pirate!"
 }
 return "I'm selling these fine leather jackets."
}

var computedProperty: String {
 get {
  if someBool {
   return "I'm a mighty pirate!"
  }
  return "I'm selling these fine leather jackets."
 }
 set {
  computedProperty = newValue
 }
 willSet {
  print("will set to \(newValue)")
 }
 didSet {
  print("did set from \(oldValue) to \(newValue)")
 }
}

class MyTableViewCell: UITableViewCell {
 static let kReuseIdentifier = String(MyTableViewCell)
 static let kCellHeight: CGFloat = 80.0
}

class PirateManager {
 static let sharedInstance = PirateManager()
 /* ... */
}

// 省略类型
doSomethingWithClosure() { response in
 print(response)
}
// 明确指出类型
doSomethingWithClosure() { response: NSURLResponse in
 print(response)
}
// map 语句使用简写
[1, 2, 3].flatMap { String($0) }

// 因为使用捕捉列表，小括号不能省略。
doSomethingWithClosure() { [weak self] (response: NSURLResponse) in
 self?.handleResponse(response)
}
// 因为返回类型，小括号不能省略。
doSomethingWithClosure() { (response: NSURLResponse) -> String in
 return String(response)
}

let completionBlock: (success: Bool) -> Void = {
 print("Success? \(success)")
}
let completionBlock: () -> Void = {
 print("Completed!")
}
let completionBlock: (() -> Void)? = nil

func readFile(withFilename filename: String) -> String? {
 guard let file = openFile(filename) else {
  return nil
 }
 let fileContents = file.read()
 file.close()
 return fileContents
}
func printSomeFile() {
 let filename = "somefile.txt"
 guard let fileContents = readFile(filename) else {
  print("不能打开 \(filename).")
  return
 }
 print(fileContents)
}

struct Error: ErrorType {
 public let file: StaticString
 public let function: StaticString
 public let line: UInt
 public let message: String
 public init(message: String, file: StaticString = #file, function: StaticString = #function, line: UInt = #line) {
  self.file = file
  self.function = function
  self.line = line
  self.message = message
 }
}

func readFile(withFilename filename: String) throws -> String {
 guard let file = openFile(filename) else {
  throw Error(message: “打不开的文件名称 \(filename).")
 }
 let fileContents = file.read()
 file.close()
 return fileContents
}
func printSomeFile() {
 do {
  let fileContents = try readFile(filename)
  print(fileContents)
 } catch {
  print(error)
 }
}

// 推荐
func eatDoughnut(atIndex index: Int) {
 guard index >= 0 && index < doughnuts else {
  // 如果 index 超出允许范围，提前返回。
  return
 }
 let doughnut = doughnuts[index]
 eat(doughnut)
}
// 不推荐
func eatDoughnuts(atIndex index: Int) {
 if index >= 0 && index < donuts.count {
  let doughnut = doughnuts[index]
  eat(doughnut)
 }
}

// 推荐
guard let monkeyIsland = monkeyIsland else {
 return
}
bookVacation(onIsland: monkeyIsland)
bragAboutVacation(onIsland: monkeyIsland)
// 不推荐
if let monkeyIsland = monkeyIsland {
 bookVacation(onIsland: monkeyIsland)
 bragAboutVacation(onIsland: monkeyIsland)
}
// 禁止
if monkeyIsland == nil {
 return
}
bookVacation(onIsland: monkeyIsland!)
bragAboutVacation(onIsland: monkeyIsland!)

// if 语句更有可读性
if operationFailed {
 return
}
// guard 语句这里有更好的可读性
guard isSuccessful else {
 return
}
// 双重否定不易被理解 - 不要这么做
guard !operationFailed else {
 return
}

// 推荐
if isFriendly {
 print("你好, 远路来的朋友！")
} else {
 print(“穷小子，哪儿来的？")
}
// 不推荐
guard isFriendly else {
 print("穷小子，哪儿来的？")
 return
}
print("你好, 远路来的朋友！")

if let monkeyIsland = monkeyIsland {
 bookVacation(onIsland: monkeyIsland)
}
if let woodchuck = woodchuck where canChuckWood(woodchuck) {
 woodchuck.chuckWood()
}

// 组合在一起因为可能立即返回
guard let thingOne = thingOne,
 let thingTwo = thingTwo,
 let thingThree = thingThree else {
 return
}
// 使用独立的语句 因为每个场景返回不同的错误
guard let thingOne = thingOne else {
 throw Error(message: "Unwrapping thingOne failed.")
}
guard let thingTwo = thingTwo else {
 throw Error(message: "Unwrapping thingTwo failed.")
}
guard let thingThree = thingThree else {
 throw Error(message: "Unwrapping thingThree failed.")
}

/**
 ## 功能列表
 这个类提供下一下很赞的功能，如下:
 - 功能 1
 - 功能 2
 - 功能 3
 ## 例子
 这是一个代码块使用四个空格作为缩进的例子。
  let myAwesomeThing = MyAwesomeClass()
  myAwesomeThing.makeMoney()
 ## 警告
 使用的时候总注意以下几点
 1. 第一点
 2. 第二点
 3. 第三点
 */
class MyAwesomeClass {
 /* ... */
}

class Pirate {
 // MARK: - 实例属性

 private let pirateName: String
 // MARK: - 初始化
 
 init() {
  /* ... */
 }
}