func giveAward(to name: String) {
    guard name == "ChuanleiGuo" else {
        print("No way!")
        return
    }
    
    print("Congratulations, \(name)!")
}
giveAward(to: "ChuanleiGuo")

func giveAward(to name: String) -> String {
    let message: String
    
    if name == "ChuanleiGuo" {
        message = "Congratulations, \(name)!"
    } else {
        message = "No way!"
    }
    
    return message
}

giveAward(to: "ChuanleiGuo")

func giveAward(to name: String?) {
    guard let winner = name else {
        print("No one won the award")
        return
    }
    
    print("Congratulations, \(winner)!")
}

for i in 1...1000 {
    guard i % 8 == 0 else { continue }
    print(i)
}

for i in 1...1000 where i % 8 == 0 {
    print(i)
}

let jsonObject : AnyObject! = NSJSONSerialization.JSONObjectWithData(dataFromTwitter, options: NSJSONReadingOptions.MutableContainers, error: nil)
if let statusesArray = jsonObject as? NSArray{
    if let aStatus = statusesArray[0] as? NSDictionary{
        if let user = aStatus["user"] as? NSDictionary{
            if let userName = user["name"] as? NSDictionary{
                
            }
        }
    }
}

public struct JSON {

}

public enum Type :Int{
    case Number      
    case String
    case Bool
    case Array
    case Dictionary
    case Null
    case Unknown     // 代表未知类型，或无法解析
}

private var _type: Type = .Null  // 初始为空类型

private var rawArray: [AnyObject] = []
private var rawDictionary: [String : AnyObject] = [:]
private var rawString: String = ""
private var rawNumber: NSNumber = 0
private var rawNull: NSNull = NSNull()

// 使用私有的 _error 来存储错误
private var _error: NSError? = nil

public var object: AnyObject {
    get {
        // 根据 _type 来取得相应的数据 
    }
    set {
        // 根据 _type 来设置相应的数据 
    }
}

public var object: AnyObject {
    get {
    
    }
    set {
        _error = nil
        switch newValue {
            case let number as NSNumber:
                if number.isBool {
                    _type = .Bool
                } else {
                    _type = .Number
                }
                self.rawNumber = number
            case  let string as String:
                _type = .String
                self.rawString = string
            case  _ as NSNull:
                _type = .Null
            case let array as [AnyObject]:
                _type = .Array
                self.rawArray = array
            case let dictionary as [String : AnyObject]:
                _type = .Dictionary
                self.rawDictionary = dictionary
            default:
                _type = .Unknown
                _error = NSError(domain: ErrorDomain, code: ErrorUnsupportedType, 
                userInfo: [NSLocalizedDescriptionKey: "It is a unsupported type"])
        }
    }
}

// 使用 NSData 来创建 JSON 
public init(data: NSData, options opt: NSJSONReadingOptions, error: NSErrorPointer)

// 使用拥有字典、数组等数据类型属性的对象来创建 JSON 
public init(_ object: AnyObject)

// 使用 [JSON] 来初始化 JSON
public init(_ jsonArray: [JSON])

// 使用 [String: JSON] 来初始化 JSON
public init(_ jsonDictionary: [String: JSON])

// 使用 JSON 字符串来初始化 JSON
public static func parse(string: String) -> JSON

public init(data:NSData, options opt: NSJSONReadingOptions = .AllowFragments, error: NSErrorPointer = nil) {
    do {
        let object: AnyObject = try NSJSONSerialization.JSONObjectWithData(data, options: opt)
        self.init(object)
    } catch let aError as NSError {
        if error != nil {
            error.memory = aError
        }
        self.init(NSNull())
    }
}

public static func parse(string: String) -> JSON {
    return string.dataUsingEncoding(NSUTF8StringEncoding)
        .flatMap({JSON(data: $0)}) ?? JSON(NSNull())
}

public init(_ object: AnyObject) {
    self.object = object
}

public init(_ jsonArray:[JSON]) {
    self.init(jsonArray.map { $0.object })
}

public init(_ jsonDictionary:[String: JSON]) {
    var dictionary = [String: AnyObject](minimumCapacity: jsonDictionary.count)
    for (key, json) in jsonDictionary {
        dictionary[key] = json.object
    }
    self.init(dictionary)
}

// StringLiteralConvertible
let json: JSON = "I'm a json"

// IntegerLiteralConvertible
let json: JSON =  12345

// FloatLiteralConvertible
let json: JSON =  2.8765

// With subscript in array
var json: JSON =  [1,2,3]

// With subscript in dictionary
var json: JSON =  ["name": "Jack", "age": 25]

// Array & Dictionary
var json: JSON =  ["name": "Jack", "age": 25, "list": ["a", "b", "c", ["what": "this"]]]

extension JSON: StringLiteralConvertible { ... }

extension JSON: IntegerLiteralConvertible { ... }

extension JSON: BooleanLiteralConvertible { ... }

extension JSON: FloatLiteralConvertible { ... }

extension JSON: DictionaryLiteralConvertible { ... }

extension JSON: ArrayLiteralConvertible { ... }

extension JSON: NilLiteralConvertible { ... }

public enum JSONKey {
    case Index(Int)
    case Key(String)
}

public protocol JSONSubscriptType {
    var jsonKey:JSONKey { get }
}

extension Int: JSONSubscriptType {
    public var jsonKey:JSONKey {
        return JSONKey.Index(self)
    }
}

extension String: JSONSubscriptType {
    public var jsonKey:JSONKey {
        return JSONKey.Key(self)
    }
}

extension JSON {
    private subscript(index index: Int) -> JSON {
        get {
            if self.type != .Array {
                var r = JSON.null
                r._error = self._error ?? NSError(domain: ErrorDomain, code: ErrorWrongType, userInfo: [NSLocalizedDescriptionKey: "Array[\(index)] failure, It is not an array"])
                return r
            } else if index >= 0 && index < self.rawArray.count {
                return JSON(self.rawArray[index])
            } else {
                var r = JSON.null
                r._error = NSError(domain: ErrorDomain, code:ErrorIndexOutOfBounds , userInfo: [NSLocalizedDescriptionKey: "Array[\(index)] is out of bounds"])
                return r
            }
        }
        set {
            if self.type == .Array {
                if self.rawArray.count > index && newValue.error == nil {
                    self.rawArray[index] = newValue.object
                }
            }
        }
    }
    
    private subscript(key key: String) -> JSON {
        get {
            var r = JSON.null
            if self.type == .Dictionary {
                if let o = self.rawDictionary[key] {
                    r = JSON(o)
                } else {
                    r._error = NSError(domain: ErrorDomain, code: ErrorNotExist, userInfo: [NSLocalizedDescriptionKey: "Dictionary[\"\(key)\"] does not exist"])
                }
            } else {
                r._error = self._error ?? NSError(domain: ErrorDomain, code: ErrorWrongType, userInfo: [NSLocalizedDescriptionKey: "Dictionary[\"\(key)\"] failure, It is not an dictionary"])
            }
            return r
        }
        set {
            if self.type == .Dictionary && newValue.error == nil {
                self.rawDictionary[key] = newValue.object
            }
        }
    }
}

private subscript(sub sub: JSONSubscriptType) -> JSON {
    get {
        switch sub.jsonKey {
        case .Index(let index): return self[index: index]
        case .Key(let key): return self[key: key]
        }
    }
    set {
        switch sub.jsonKey {
        case .Index(let index): self[index: index] = newValue
        case .Key(let key): self[key: key] = newValue
        }
    }
}

public subscript(path: [JSONSubscriptType]) -> JSON {
    get {
        return path.reduce(self) { $0[sub: $1] }
    }
    set {
        switch path.count {
        case 0:
            return
        case 1:
            self[sub:path[0]].object = newValue.object
        default:
            var aPath = path; aPath.removeAtIndex(0)
            var nextJSON = self[sub: path[0]]
            nextJSON[aPath] = newValue
            self[sub: path[0]] = nextJSON
        }
    }
}

public subscript(path: JSONSubscriptType...) -> JSON {
    get {
        return self[path]
    }
    set {
        self[path] = newValue
    }
}

let name = json[9]["list"]["person"]["name"]

let sameName = json[9,"list","person","name"]

// MARK: - Array
extension JSON {
    public var array: [JSON]? { get }     // 返回 Optional([JSON])
    public var arrayValue: [JSON] { get } // 返回 [JSON]
}

// MARK: - Dictionary
extension JSON {
    public var dictionary: [String: JSON]? { get }
    public var dictionaryValue: [String: JSON] { get }
}

// MARK: - Array
extension JSON {
    //Optional [AnyObject]
    public var arrayObject: [AnyObject]? {
        get {
            switch self.type {
            case .Array:
                return self.rawArray
            default:
                return nil
            }
        }
        set {
            if let array = newValue {
                self.object = array
            } else {
                self.object = NSNull()
            }
        }
    }
}

// MARK: - Dictionary
extension JSON {
    //Optional [String : AnyObject]
    public var dictionaryObject: [String : AnyObject]? {
        get {
            switch self.type {
            case .Dictionary:
                return self.rawDictionary
            default:
                return nil
            }
        }
        set {
            if let v = newValue {
                self.object = v
            } else {
                self.object = NSNull()
            }
        }
    }
}

// MARK: - Number
extension JSON {

    //Optional number
    public var number: NSNumber? {
        get {
            switch self.type {
            case .Number, .Bool:
                return self.rawNumber
            default:
                return nil
            }
        }
        set {
            self.object = newValue ?? NSNull()
        }
    }

    //Non-optional number
    public var numberValue: NSNumber {
        get {
            switch self.type {
            case .String:
                let decimal = NSDecimalNumber(string: self.object as? String)
                if decimal == NSDecimalNumber.notANumber() {  // indicates parse error
                    return NSDecimalNumber.zero()
                }
                return decimal
            case .Number, .Bool:
                return self.object as? NSNumber ?? NSNumber(int: 0)
            default:
                return NSNumber(double: 0.0)
            }
        }
        set {
            self.object = newValue
        }
    }
}

extension JSON {
    public var double: Double? {
        get {
            return self.number?.double
        }
        set {
            if let newValue = newValue {
                self.object = NSNumber(double: newValue)
            } else {
                self.object = NSNull()
            }
        }
    }
    
    public var doubleValue: Double {
        get {
            return self.numberValue.doubleValue
        } 
        set {
            self.object = NSNumber(double: newValue)
        }
    }
}

// MARK: - URL
extension JSON {
    public var URL: NSURL? { get }
}

extension JSON: RawRepresentable {
    public init?(rawValue: AnyObject) {
        if JSON(rawValue).type == .Unknown {
            return nil
        } else {
            self.init(rawValue)
        }
    }

    public var rawValue: AnyObject {
        return self.object
    }
}

extension JSON {
    public func rawData(options opt: NSJSONWritingOptions = NSJSONWritingOptions(rawValue: 0)) throws -> NSData {
        guard NSJSONSerialization.isValidJSONObject(self.object) else {
            throw NSError(domain: ErrorDomain, code: ErrorInvalidJSON, userInfo: [NSLocalizedDescriptionKey: "JSON is invalid"])
        }

        return try NSJSONSerialization.dataWithJSONObject(self.object, options: opt)
    }
}

// 我们可以简单地将 JSON 对象转化为 NSData
if let data = json.rawData() {
    //Do something you want
}

extension JSON {
    public func rawString(encoding: UInt = NSUTF8StringEncoding, options opt: NSJSONWritingOptions = .PrettyPrinted) -> String? {
        switch self.type {
        case .Array, .Dictionary:
            do {
                let data = try self.rawData(options: opt)
                return NSString(data: data, encoding: encoding) as? String
            } catch _ {
                return nil
            }
        case .String:
            return self.rawString
        case .Number:
            return self.rawNumber.stringValue
        case .Bool:
            return self.rawNumber.boolValue.description
        case .Null:
            return "null"
        default:
            return nil
        }
    }
}

// 我们可以简单地将 JSON 对象转化为 String
if let string = json.rawString() {
    //Do something you want
}

extension JSON: Printable, DebugPrintable { ... }

extension JSON: CollectionType {
    public typealias Generator = JSONGenerator
    
    public typealias Index = JSONIndex
    
    public func generate() -> JSON.Generator {
        return JSON.Generator(self)
    }
}

extension JSON: CollectionType {
    public var startIndex: JSON.Index {
        switch self.type {
        case .Array:
            return JSONIndex(arrayIndex: self.rawArray.startIndex)
        case .Dictionary:
            return JSONIndex(dictionaryIndex: self.rawDictionary.startIndex)
        default:
            return JSONIndex()
        }
    }
    
    public var endIndex: JSON.Index {
        switch self.type {
        case .Array:
            return JSONIndex(arrayIndex: self.rawArray.endIndex)
        case .Dictionary:
            return JSONIndex(dictionaryIndex: self.rawDictionary.endIndex)
        default:
            return JSONIndex()
        }
    }
    
    public subscript (position: JSON.Index) -> JSON.Generator.Element {
        switch self.type {
        case .Array:
            return (String(position.arrayIndex), JSON(self.rawArray[position.arrayIndex!]))
        case .Dictionary:
            let (key, value) = self.rawDictionary[position.dictionaryIndex!]
            return (key, JSON(value))
        default:
            return ("", JSON.null)
        }
    }
    
    public var isEmpty: Bool {
        get {
            switch self.type {
            case .Array:
                return self.rawArray.isEmpty
            case .Dictionary:
                return self.rawDictionary.isEmpty
            default:
                return true
            }
        }
    }
    
    public var count: Int {
        switch self.type {
        case .Array:
            return self.rawArray.count
        case .Dictionary:
            return self.rawDictionary.count
        default:
            return 0
        }
    }
    
    public func underestimateCount() -> Int {
        switch self.type {
        case .Array:
            return self.rawArray.underestimateCount()
        case .Dictionary:
            return self.rawDictionary.underestimateCount()
        default:
            return 0
        }
    }
}

public struct JSONGenerator: GeneratorType {
    // 生成元素的类型为(String, JSON)
    public typealias Element = (String, JSON)

    private let type: Type
    private var dictionayGenerate: DictionaryGenerator<String, AnyObject>?
    private var arrayGenerate: IndexingGenerator<[AnyObject]>?
    private var arrayIndex: Int = 0      // 当生成器生成数组元素时，保存数组索引
    
    init(_ json: JSON) {
        self.type = json.type
        if type == .Array {
            self.arrayGenerate = json.rawArray.generate()
        }else {
            self.dictionayGenerate = json.rawDictionary.generate()
        }
    }
}

public mutating func next() -> JSONGenerator.Element? {
    switch self.type {
    case .Array:
        if let o = self.arrayGenerate?.next() {
            let i = self.arrayIndex
            self.arrayIndex += 1
            return (String(i), JSON(o))
        } else {
            return nil
        }
    case .Dictionary:
        if let (k, v): (String, AnyObject) = self.dictionayGenerate?.next() {
            return (k, JSON(v))
        } else {
            return nil
        }
    default:
        return nil
    }
}

public struct JSONIndex {
    let arrayIndex: Int?
    let dictionaryIndex: DictionaryIndex<String, AnyObject>?

    let type: Type

    init(){
        self.arrayIndex = nil
        self.dictionaryIndex = nil
        self.type = .Unknown
    }

    init(arrayIndex: Int) {
        self.arrayIndex = arrayIndex
        self.dictionaryIndex = nil
        self.type = .Array
    }

    init(dictionaryIndex: DictionaryIndex<String, AnyObject>) {
        self.arrayIndex = nil
        self.dictionaryIndex = dictionaryIndex
        self.type = .Dictionary
    }
}

extension JSONIndex: ForwardIndexType {
    public func successor() -> JSONIndex {
        switch self.type {
        case .Array:
            return JSONIndex(arrayIndex: self.arrayIndex!.successor())
        case .Dictionary:
            return JSONIndex(dictionaryIndex: self.dictionaryIndex!.successor())
        default:
            return JSONIndex()
        }
    }
}

extension JSONIndex: Equatable, Comparable {}

public func ==(lhs: JSONIndex, rhs: JSONIndex) -> Bool {
    switch (lhs.type, rhs.type) {
    case (.Array, .Array):
        return lhs.arrayIndex == rhs.arrayIndex
    case (.Dictionary, .Dictionary):
        return lhs.dictionaryIndex == rhs.dictionaryIndex
    default:
        return false
    }
}

public func <(lhs: JSONIndex, rhs: JSONIndex) -> Bool {
    switch (lhs.type, rhs.type) {
    case (.Array, .Array):
        return lhs.arrayIndex < rhs.arrayIndex
    case (.Dictionary, .Dictionary):
        return lhs.dictionaryIndex < rhs.dictionaryIndex
    default:
        return false
    }
}

public func <=(lhs: JSONIndex, rhs: JSONIndex) -> Bool {
    switch (lhs.type, rhs.type) {
    case (.Array, .Array):
        return lhs.arrayIndex <= rhs.arrayIndex
    case (.Dictionary, .Dictionary):
        return lhs.dictionaryIndex <= rhs.dictionaryIndex
    default:
        return false
    }
}

public func >=(lhs: JSONIndex, rhs: JSONIndex) -> Bool {
    switch (lhs.type, rhs.type) {
    case (.Array, .Array):
        return lhs.arrayIndex >= rhs.arrayIndex
    case (.Dictionary, .Dictionary):
        return lhs.dictionaryIndex >= rhs.dictionaryIndex
    default:
        return false
    }
}

public func >(lhs: JSONIndex, rhs: JSONIndex) -> Bool {
    switch (lhs.type, rhs.type) {
    case (.Array, .Array):
        return lhs.arrayIndex > rhs.arrayIndex
    case (.Dictionary, .Dictionary):
        return lhs.dictionaryIndex > rhs.dictionaryIndex
    default:
        return false
    }
}