// 这个是CELL的宽度和高度，可以通过计算
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAtIndexPath indexPath: NSIndexPath) -> CGSize {
    return CGSizeMake(yourWidth, yourHeight)
}

// collectionView的上下左右间距
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, insetForSectionAtIndex section: Int) -> UIEdgeInsets {
    return UIEdgeInsets(top: 0, left: 10, bottom: 0, right: 10)
}

// 每个小单元的间距
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAtIndex section: Int) -> CGFloat {
    return 0
}

// 单元的行间距
func collectionView(collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAtIndex section: Int) -> CGFloat {
    return CGFloat(20.0)
}

let score: [Int?] = [99, 100, nil, 60]
score.forEach {
    if let s = $0 where s == 100 {
        print("you are so smart!")
    }
}

// 每个 section 显示 cell 的数量
func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
    return 7
}
// 每个 view 显示 section 的数量
func numberOfSections(in collectionView: UICollectionView) -> Int {
    return 3
}

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate, UITabBarControllerDelegate {

    var window: UIWindow?

    func application(application: UIApplication,
        didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
    }
    // 实现其他protocol
}

@IBAction func enter(sender: UIButton) {
    let flowLayout = UICollectionViewFlowLayout()

    flowLayout.minimumLineSpacing = 20
    flowLayout.minimumInteritemSpacing = 10
    flowLayout.itemSize = CGSize(width: 80, height: 120)
    flowLayout.scrollDirection = .Vertical

    flowLayout.sectionInset = UIEdgeInsets(top: 10, left: 20, bottom: 10, right: 20)

    // 这个collection如果是本地变量可能会被回收，造成这个view闪一下就不见了。
    collection = CollectionViewController(collectionViewLayout: flowLayout)
    self.view.addSubview(collection!.view)
}

// http://blog.csdn.net/crystal300/article/details/52690994
// swift 3.0
func transferStringToColor(_ colorStr:String) -> UIColor {

    var color = UIColor.black
    var cStr : String = colorStr.trimmingCharacters(in: CharacterSet.whitespacesAndNewlines).uppercased()

    if cStr.hasPrefix("#") {
        let index = cStr.index(after: cStr.startIndex)
        cStr = cStr.substring(from: index)
    }
    if cStr.characters.count != 6 {
        return color
    }

    let rRange = cStr.startIndex ..< cStr.index(cStr.startIndex, offsetBy: 2)
    let rStr = cStr.substring(with: rRange)

    let gRange = cStr.index(cStr.startIndex, offsetBy: 2) ..< cStr.index(cStr.startIndex, offsetBy: 4)
    let gStr = cStr.substring(with: gRange)

    let bIndex = cStr.index(cStr.endIndex, offsetBy: -2)
    let bStr = cStr.substring(from: bIndex)

    var r:CUnsignedInt = 0, g:CUnsignedInt = 0, b:CUnsignedInt = 0;
    Scanner(string: rStr).scanHexInt32(&r)
    Scanner(string: gStr).scanHexInt32(&g)
    Scanner(string: bStr).scanHexInt32(&b)

    color = UIColor(red: CGFloat(r) / 255.0, green: CGFloat(g) / 255.0, blue: CGFloat(b) / 255.0, alpha: CGFloat(1))

    return color
}

// swift 2.3
func transferStringToColor(colorStr: String, alpha: CGFloat = 1.0) -> UIColor {
    let color = UIColor.blackColor()
    var cStr: String = colorStr.stringByTrimmingCharactersInSet(NSCharacterSet.whitespaceAndNewlineCharacterSet()).uppercaseString

    if cStr.hasPrefix("#") {
        let index = cStr.startIndex.advancedBy(1)
        cStr = cStr.substringFromIndex(index)
    }

    if cStr.characters.count == 3 {
        cStr = cStr.characters.reduce("", combine: { $0 + String([$1, $1]) })
    }

    if cStr.characters.count != 6 {
        return color
    }

    let rRange=Range<String.Index>(start: cStr.startIndex, end: cStr.startIndex.advancedBy(2))
    let rStr = cStr[rRange]

    let gRange=Range<String.Index>(start: cStr.startIndex.advancedBy(2), end: cStr.startIndex.advancedBy(4))
    let gStr = cStr[gRange]

    let bRange=Range<String.Index>(start: cStr.startIndex.advancedBy(4), end: cStr.startIndex.advancedBy(6))
    let bStr = cStr[bRange]

    var r: CUnsignedInt = 0, g: CUnsignedInt = 0, b: CUnsignedInt = 0

    NSScanner(string: rStr).scanHexInt(&r)
    NSScanner(string: gStr).scanHexInt(&g)
    NSScanner(string: bStr).scanHexInt(&b)

    return UIColor(red: CGFloat(r) / 255.0, green: CGFloat(g) / 255.0, blue: CGFloat(b) / 255.0, alpha: alpha)
}

let storyBoard = UIStoryboard(name: "ServiceStoryboard", bundle: nil)
let vc = storyBoard.instantiateViewController(withIdentifier: "servicePage")

let constraint = NSLayoutConstraint(
    // view1
    item: view1,
    attribute: NSLayoutAttribute.Trailing,
    relatedBy: NSLayoutRelation.Equal,
    // view2
    toItem: view2,
    attribute: NSLayoutAttribute.Trailing,

    multiplier: 1,
    constant: 10
)

someView.addConstraint(constraint)
// view1.att1 (related = <= >=) view2.attr * multiplier + constant
// 注意，当不需要第二个属性（toItem 为 nil）的时候，应该设置为 .NotAnAttribute，否则会报错

let MAX = 10
Int(arc4random() % MAX)

// 这样写可能会导致 Xcode indexing 假死
struct Objects {
    let objectA = [
        "text1",
        "text2",
        "text3",
        "text4"
    ]
}

// 需要改成这样
struct Objects {
    let objectA = [ "text1",  "text2",  "text3",  "text4"]
}

// 简直无语

@IBDesignable
class IconButtonViewController: UIViewController {
    这样在File's Owner Attribute面板中就会增加一个Test属性
    @IBInspectable var test:String
}

// 第二个参数是纳秒，10e-9秒
let time = dispatch_time(DISPATCH_TIME_NOW, Int64(5e8))
dispatch_after(time, dispatch_get_global_queue(0, 0)) { () -> Void in
    self.scrollView.contentSize = {
        let height = self.middleContainer.frame.size.height + self.imageView.frame.size.height
        let size = CGSize(width: self.view.frame.size.width, height: height)
        return size
    }()
}

func makeGestureAvailable(){
    if let gestureArray = self.navigationController?.view.gestureRecognizers {  // 这里的view换成自己的view
        gestureArray.forEach({ (gesture) in
            if gesture.isKindOfClass(UIScreenEdgePanGestureRecognizer) {
                self.scrollView.panGestureRecognizer.requireGestureRecognizerToFail(gesture)
            }
        })
    }
}

let greeting = "Guten Tag!"
greeting[greeting.startIndex]
// G
greeting[greeting.index(before: greeting.endIndex)]
// !
greeting[greeting.index(after: greeting.startIndex)]
// u
let index = greeting.index(greeting.startIndex, offsetBy: 7)
greeting[index] // 注意使用方式
// a

func toHexString(int: Int) -> String{
    let highHex = int / 16 % 16
    let lowHex = int % 16
    let charList = "0123456789ABCDEF"
    let highIndex = charList.index(charList.startIndex, offsetBy: highHex)
    let lowIndex = charList.index(charList.startIndex, offsetBy: lowHex)
    return "\(charList[highIndex])\(charList[lowIndex])"
}

"hello".data(using: String.Encoding.isoLatin1, allowLossyConversion: false) // 这个false是什么？
String(data: Data([0x68, 0x65, 0x6C, 0x6C 0x6F]), encoding: String.Encoding.isoLatin1)

// AppDelegate
func application(application: UIApplication, didRegisterForRemoteNotificationsWithDeviceToken deviceToken: NSData) {
    // deviceToken 转字符串
    let token:String = deviceToken.map { String(format: "%02x", $0) }.joined().uppercased()
    print("token==\(token)")
}

func registerNofitication() {
    UIApplication.shared.registerForRemoteNotifications()
}

func application(_ application: UIApplication, didRegister notificationSettings: UIUserNotificationSettings) {
    self.registerNofitication()
}