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代码

OptionSet​

需求：用户通过点击按钮，回答问卷，可多选。

struct Answers: OptionSet {
    let rawValue: Int

    static let A = Answers(rawValue: 1 << 0)
    static let B = Answers(rawValue: 1 << 1)
    static let C = Answers(rawValue: 1 << 2)
    static let D = Answers(rawValue: 1 << 3)
    static let E = Answers(rawValue: 1 << 4)
    static let F = Answers(rawValue: 1 << 5)
    static let G = Answers(rawValue: 1 << 5)
    static let H = Answers(rawValue: 1 << 5)

    static let all: Answers = [.A, .B, .C, .D, .E, .F, .G, .H]
}

We can pass .all instead of [.all] if we want to select all answers. The reason for this is that OptionSet is an object that can be initialized using an array literal but it is not an array. Instead, it is an object that stands on its own and it uses a single raw value to represent all options that it holds.

let singleOption: ShippingOptions = .priority
let multipleOptions: ShippingOptions = [.nextDay, .secondDay, .priority]
let noOptions: ShippingOptions = []
var freeOptions: ShippingOptions = []
freeOptions.insert(.priority)
if freeOptions.contains(.priority) {}

用 python 打印出 100111 对应的选项 ABCF：

base = 65
for i in range(0, 64):
    string = "{0:b}".format(i)
    N = len(string)
    res = str(i) + " "
    for j in range(N-1, -1, -1):
        if string[j] == '1':
            res += str(chr(base + N-j-1))
    print(res)

String​

是否匹配正则表达式：

var str = "HelloaZ0123___"
var str2 = "Hello, playground"
var str3 = "Hello???"

extension String {
    // 是否匹配正则表达式
    func matchRegex(_ pattern: String) -> Bool {
        guard let regex = try? NSRegularExpression(pattern: pattern, options: []) else { return false }
        let matches = regex.matches(in: self, options: [], range: NSRange(location: 0, length: self.count))
        return matches.count > 0
    }
}

str.matchRegex("^[A-Za-z0-9_]+$") // true
str2.matchRegex("^[A-Za-z0-9_]+$") // false
str3.matchRegex("^[A-Za-z0-9_]+$") // false

过滤，只允许数字、字母、小数点、下划线：

let str = "1A_2b_$9.99_¥8.88"
let set = CharacterSet.alphanumerics.union(CharacterSet.init(charactersIn: "_."))
let filted = String(v.unicodeScalars.filter(set.contains))

将秒数转换为时间字符串：

func ms(from count: Int) -> (String, String) {
    let minute = count / 60
    let second = count - minute * 60
    var minuteStr = "\(minute)"
    if minuteStr.count == 1 {
        minuteStr = "0\(minuteStr[0])"
    }
    var secondStr = "\(second)"
    if secondStr.count == 1 {
        secondStr = "0\(secondStr[0])"
    }
    return (minuteStr, secondStr)
}

将秒数转换为 00:00 格式：

func str(from seconds: Int) -> String {
    let minute = seconds / 60
    let second = seconds - minute * 60
    var minuteStr = "\(minute)"
    if minuteStr.count == 1 {
        minuteStr = "0\(String(minuteStr.prefix(1)))"
    }
    var secondStr = "\(second)"
    if secondStr.count == 1 {
        secondStr = "0\(String(secondStr.prefix(1)))"
    }
    return "\(minuteStr):\(secondStr)"
}

计算 MD5：

extension String {
    var md5: String {
        guard !isEmpty else { return "" }
        // Create and initialize MD5 context:
        var context = CC_MD5_CTX()
        CC_MD5_Init(&context)
        let data = Data(self.utf8)
        // Read data and update MD5 context:
        data.withUnsafeBytes {
            _ = CC_MD5_Update(&context, $0.baseAddress, numericCast(data.count))
        }
        var digest: [UInt8] = Array(repeating: 0, count: Int(CC_MD5_DIGEST_LENGTH))
        _ = CC_MD5_Final(&digest, &context)
        let hex = digest.map { String(format: "%02hhx", $0) }.joined()
        return hex
    }
}

extension URL {
    var md5: String {
        return self.absoluteString.md5
    }
}

计算字符串的宽高：

extension String {
    func width(font: UIFont) -> CGFloat {
        return self.size(withAttributes: [.font: font]).width
    }

    func height(withConstrainedWidth width: CGFloat, font: UIFont) -> CGFloat {
        let constraintRect = CGSize(width: width, height: .greatestFiniteMagnitude)
        let boundingBox = self.boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, attributes: [.font: font], context: nil)

        return ceil(boundingBox.height)
    }

    func width(withConstrainedHeight height: CGFloat, font: UIFont) -> CGFloat {
        let constraintRect = CGSize(width: .greatestFiniteMagnitude, height: height)
        let boundingBox = self.boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, attributes: [.font: font], context: nil)

        return ceil(boundingBox.width)
    }
}

Foundation​

URL​

拼接参数到链接里：

var domain = "https://github.com"
var params = ["device": "iOS", "systemVersion": "13.2.2"]
var query = "?"
params.forEach { (key, value) in
    if let valueWithPercentEncoding = value.addingPercentEncoding(withAllowedCharacters: .alphanumerics) {
        query += key
        query += "="
        query += valueWithPercentEncoding
        query += "&"
    }
}
if query.last == "&" {
    query.removeLast()
}
print(domain + query)

if let url = URL(string: domain + query), let components = URLComponents(url: url, resolvingAgainstBaseURL: true), let queryItems = components.queryItems {
    var dict = [String: Any]()
    for item in queryItems {
        dict[item.name] = item.value
    }
}

URLSession​

断点续传：

/// 下载模型，实现了 URLSessionDataDelegate 用于断点续传
class NetworkDownloadModel: NSObject, URLSessionDataDelegate {
    /// 下载的 URL
    private var url: URL
    /// 下载文件的存放路径（注意带.temp后缀）
    private var destination: URL
    /// 临时文件，下载成功后再移到目的地
    private var tempDestination: URL
    /// 下载完成的回调
    private var completion: (Error?) -> Void
    /// 文件处理
    private var fileHandle: FileHandle?

    init(url: URL, destination: URL, completion: @escaping (Error?) -> Void) {
        self.url = url
        self.destination = destination
        self.completion = completion
        // 目的地创建一个tmp文件夹用于存放文件
        let tmp = destination.deletingLastPathComponent().appendingPathComponent("tmp")
        try? FileManager.default.createDirectory(at: tmp, withIntermediateDirectories: true, attributes: nil)
        self.tempDestination = tmp.appendingPathComponent(destination.lastPathComponent)
        super.init()
    }

    /// 执行下载任务
    ///
    /// - Parameter resumeAtBreakPoint: 是否断点续传
    @discardableResult
    func download(resumeAtBreakPoint: Bool) -> URLSessionDataTask {
        // 已下载的字节数
        var downloadedBytes: UInt64 = 0
        // 不断点续传的话，删掉旧的文件。
        if !resumeAtBreakPoint {
            try? FileManager.default.removeItem(at: tempDestination)
        }
        if FileManager.default.fileExists(atPath: tempDestination.path) {
            // 如果已经下载过，取得已下载的字节数
            if let fileDict = try? FileManager.default.attributesOfItem(atPath: tempDestination.path) as NSDictionary {
                downloadedBytes = fileDict.fileSize()
            }
        } else {
            // 如果未下载过，创建文件用于断点续传
            FileManager.default.createFile(atPath: tempDestination.path, contents: nil, attributes: nil)
        }
        var urlRequest = URLRequest(url: url)
        // 断点续传的 header
        if downloadedBytes > 0 {
            urlRequest.setValue("bytes=\(downloadedBytes)-", forHTTPHeaderField: "Range")
        }

        let configuration = URLSessionConfiguration.default
        configuration.httpMaximumConnectionsPerHost = 1
        let session = URLSession(configuration: configuration, delegate: self, delegateQueue: nil)
        let task = session.dataTask(with: urlRequest)
        task.resume()
        return task
    }

    // MARK: URLSessionDataDelegate
    func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive response: URLResponse, completionHandler: @escaping (URLSession.ResponseDisposition) -> Void) {
        if let httpResponse = response as? HTTPURLResponse {
            if (200...299).contains(httpResponse.statusCode) {
                fileHandle = try? FileHandle(forUpdating: tempDestination)
                completionHandler(.allow)
            }
            else {
                try? FileManager.default.removeItem(at: tempDestination) // 出现服务器异常，删除旧的临时文件
                completionHandler(.cancel)
                completion(NSError(domain: "", code: httpResponse.statusCode, userInfo: nil))
            }
        }
    }

    func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) {
        fileHandle?.seekToEndOfFile()
        fileHandle?.write(data)
    }

    // 请求结束
    func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
        fileHandle?.closeFile()
        if error == nil {
            try? FileManager.default.moveItem(at: tempDestination, to: destination)
        }
        completion(error)
    }
}

失败重试：

func retry(times: Int, data: Data) {
    if times == 0 {
        return
    }
    upload(data, success: {}, failure: { error in
        retry(times: times - 1, data: data)
    })
}

JSONSerialization​

// 从bundle中读取一个json文件
if let url = Bundle.main.url(forResource: "stickers", withExtension: "json"),
    let data = try? Data(contentsOf: url),
    let jsonObject = try? JSONSerialization.jsonObject(with: data),
    let json = jsonObject as? [String: Any] {
     // ...
}

// json 字符串转成字典
if let data = json.data(using: .utf8), let dict = try? JSONSerialization.jsonObject(with: data, options: []) as? [String: Any] {
    logEventCount(code, dict: dict)
}

文件目录​

var DocumentDirectory: URL {
    return FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
//    return NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true).first!
}

var CacheDirectory: URL {
    return FileManager.default.urls(for: .cachesDirectory, in: .userDomainMask).first!
}

func VideoDirectory() -> URL {
    let url = DocumentDirectory.appendingPathComponent("Video", isDirectory: true)
    // create folder if not exist
    try? FileManager.default.createDirectory(at: url, withIntermediateDirectories: true, attributes: nil)
    return url
}

Bundle​

private let appVersion = Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String ?? "1.0"
private let buildVersion = Bundle.main.object(forInfoDictionaryKey: "CFBundleVersion") as? String ?? "1"
private let osVersion = UIDevice.current.systemVersion
private let deviceString = DeviceGuru().hardwareString() // dependency: DeviceGuru
private let idfv = UIDevice.current.identifierForVendor?.uuidString
private let systemLanguage = Locale.preferredLanguages.first // 设置 - 通用 - 语言与地区 - 首选语言顺序（第一位）
private let regionCode = Locale.current.regionCode // 国家或地区
UIDevice.current.isBatteryMonitoringEnabled = true

Date​

获取当前时间：

private func getCurrentDate() -> String {
    let dateFormater = DateFormatter()
    dateFormater.dateFormat = "yyyyMMdd"
    return dateFormater.string(from: Date())
}

设置 UIDatePicker 时间为晚上 8 点：

picker.datePickerMode = .time
let calendar = Calendar.current
var components = DateComponents()
components.hour = 20
components.minute = 0
picker.setDate(calendar.date(from: components)!, animated: false)

ISO 8601：是国际标准化组织的日期和时间的表示方法。

RFC 3339: This document defines a date and time format for use in Internet protocols that is a profile of the ISO 8601 standard for representation of dates and times using the Gregorian calendar.

日期格式：https://nsdateformatter.com/

Date 对象使用 +0 时区

let now = Date()
print(now) // 2020-07-16 07:12:02 +0000

Date 转 String

let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
dateFormatter.locale = Locale.current
let dateString = dateFormatter.string(from: now)
print(dateString) // 2020-07-16 15:15:17

根据用户的时区将 Date 转换为 Calendar

var calendar = Calendar.current
calendar.timeZone = TimeZone.current
let dateComponents = calendar.dateComponents([.year, .month, .day], from: now)
print(dateComponents) // year: 2020 month: 7 day: 16 isLeapMonth: false

初始化一个特定日期

// 初始化一个日期
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZ"
if let date617 = dateFormatter.date(from: "2020-06-17T23:59:59+0000") {
    print(date617)
}

NSAttributedString​

// 字间距
let tryText = "TRY FOR FREE!!!"
let tryTextMark = "!!!"
let substringRange = tryText.range(of: tryTextMark)!
let nsRange = NSRange(substringRange, in: tryText)
let attrStr = NSMutableAttributedString(string: tryText)
attrStr.addAttribute(NSAttributedString.Key.kern, value: -5, range: nsRange)
tryLabel.attributedText = attrStr
tryLabel.font = UIFont.systemFont(ofSize: 40 * kAppScale, weight: .heavy)
tryLabel.textColor = UIColor.white

let line1 = "Your Meditation Program\n"
let line2 = "Listen to meditation audio for weight-loss"
let attrString = NSMutableAttributedString(string: line1 + line2)

// 字体及颜色
attrString.addAttribute(.font, value: UIFont.systemFont(ofSize: 24 * kAppScale375, weight: .heavy), range: NSRange(location: 0, length: line1.count))
attrString.addAttribute(.foregroundColor, value: UIColor.black, range: NSRange(location: 0, length: line1.count))
attrString.addAttribute(.font, value: UIFont.systemFont(ofSize: 14 * kAppScale375, weight: .bold), range: NSRange(location: line1.count, length: line2.count))
attrString.addAttribute(.foregroundColor, value: UIColor.black, range: NSRange(location: line1.count, length: line2.count))

// 斜体
attrString.addAttribute(NSAttributedString.Key.obliqueness, value: 0.2, range: NSRange(location: line1.count, length: line2.count))

// 行间距
let style = NSMutableParagraphStyle()
style.lineSpacing = 10.0
attrString.addAttribute(.paragraphStyle, value: style, range: NSRange(location: 0, length: line1.count + line2.count))

self.listenLabel.attributedText = attrString

UIViewController​

UITabBarController​

圆角 TabBar

class TabBarController: UITabBarController, UITabBarControllerDelegate {

    override func viewDidLoad() {
        super.viewDidLoad()

        let sleep = ("sleep_icon_normal", "sleep_icon_hover", "Sleep")
        let sounds = ("sounds_icon_normal", "sounds_icon_hover", "Sounds")
        let more = ("more_icon_normal", "more_icon_hover", "More")
        let tabTuples = [sleep, sounds, more]

        var viewControllers = [UIViewController]()
        for i in 0 ..< tabTuples.count {
            let vc = ViewController()
            let nav = UINavigationController(rootViewController: vc)
            nav.tabBarItem.image = UIImage(named: tabTuples[i].0)
            nav.tabBarItem.selectedImage = UIImage(named: tabTuples[i].1)
            nav.tabBarItem.title = tabTuples[i].2
            viewControllers.append(nav)
        }

        self.viewControllers = viewControllers
        self.selectedIndex = 0
        self.tabBar.tintColor = UIColor.white
        self.tabBar.unselectedItemTintColor = UIColor.white.withAlphaComponent(0.42)
        self.tabBar.backgroundColor = UIColor(red: 16/255, green: 16/255, blue: 16/255, alpha: 1)
        self.tabBar.backgroundImage = UIImage.from(color: .clear)
        self.tabBar.shadowImage = UIImage()
    }

    override func viewWillLayoutSubviews() {
        let cornerRadius: CGFloat = 30.0
        if #available(iOS 11.0, *) {
            self.tabBar.layer.maskedCorners = [.layerMinXMinYCorner, .layerMaxXMinYCorner]
            self.tabBar.layer.cornerRadius = cornerRadius
        } else {
            let bezierpath = UIBezierPath.init(roundedRect: self.tabBar.bounds, byRoundingCorners: [UIRectCorner.topLeft, UIRectCorner.topRight], cornerRadii: CGSize(width: cornerRadius, height: cornerRadius))
            let shape = CAShapeLayer()
            shape.path = bezierpath.cgPath
            self.tabBar.layer.mask = shape
        }
    }
}

UIAlertController​

let alert = UIAlertController(title: "", message: "", preferredStyle: .alert)
let cancel = UIAlertAction(title: "", style: .cancel) { (action) in
}
let ok = UIAlertAction(title: "", style: .default) { (action) in
}
alert.addAction(cancel)
alert.addAction(ok)
alert.preferredAction = ok
self.parentViewController?.present(alert, animated: true, completion: nil)

UINavigationController​

解决 push 和 pop 时动画卡顿问题：

// 背景图片的contentMode不对
if let path = Bundle.main.path(forResource: "skin_preview_background", ofType: "png"), let image = UIImage(contentsOfFile: path) {
    let imageView = UIImageView(frame: view.bounds)
    imageView.image = image
    imageView.contentMode = .scaleToFit
    view.addSubview(imageView)
}

// 当前vc的背景色设为白色
self.view.backgroundColor = .white

UIView​

tableHeaderView, tableFooterView​

extension UIView { /// 创建一个占位的 UIView，这是用于 tableHeaderView 和 tableFooterView /// When assigning a view to this property, set the height of that view to a nonzero value. /// 否则，tableHeaderView 和 tableFooterView 的高度会无法正确刷新 static func tableHeaderFooterPlaceholder() -> UIView { return UIView(frame: CGRect(x: 0, y: 0, width: CGFloat.leastNormalMagnitude, height: CGFloat.leastNormalMagnitude)) } }

圆角​

override func layoutSubviews() {
    let cornerRadius: CGFloat = 20
    if #available(iOS 11.0, *) {
        self.layer.maskedCorners = [.layerMinXMinYCorner, .layerMaxXMinYCorner]
        self.layer.cornerRadius = cornerRadius
    } else {
        let bezierpath = UIBezierPath.init(roundedRect: self.bounds, byRoundingCorners: [UIRectCorner.topLeft, UIRectCorner.topRight], cornerRadii: CGSize(width: cornerRadius, height: cornerRadius))
        let shape = CAShapeLayer()
        shape.path = bezierpath.cgPath
        self.layer.mask = shape
    }
}

UILabel​

带内边距：

@IBDesignable class URLabel: UILabel {
    @IBInspectable var topInset: CGFloat = 0
    @IBInspectable var bottomInset: CGFloat = 0
    @IBInspectable var leftInset: CGFloat = 4
    @IBInspectable var rightInset: CGFloat = 4

    override func drawText(in rect: CGRect) {
        let insets = UIEdgeInsets(top: topInset, left: leftInset, bottom: bottomInset, right: rightInset)
        super.drawText(in: rect.inset(by: insets))
    }

    override var intrinsicContentSize: CGSize {
        let size = super.intrinsicContentSize
        return CGSize(width: size.width + leftInset + rightInset,
                      height: size.height + topInset + bottomInset)
    }

    override var bounds: CGRect {
        didSet {
            // ensures this works within stack views if multi-line
            preferredMaxLayoutWidth = bounds.width - (leftInset + rightInset)
        }
    }
}

UIButton​

图片在上面，文字在下面：

extension UIButton {
    func centerVertically(padding: CGFloat = 6.0) {
        guard let imageViewSize = currentImage?.size, let titleLabelSize = titleLabel?.intrinsicContentSize else { return }
        imageEdgeInsets = UIEdgeInsets.only(top: -(titleLabelSize.height + padding), right: -titleLabelSize.width)
        titleEdgeInsets = UIEdgeInsets.only(left: -imageViewSize.width, bottom: -(imageViewSize.height + padding))
    }
}

扩大点击区域：

private var pTouchAreaEdgeInsets: UIEdgeInsets = .zero
extension UIButton {
    public var touchAreaEdgeInsets: UIEdgeInsets {
        get {
            if let value = objc_getAssociatedObject(self, &pTouchAreaEdgeInsets) as? NSValue {
                var edgeInsets: UIEdgeInsets = .zero
                value.getValue(&edgeInsets)
                return edgeInsets
            }
            else {
                return .zero
            }
        }
        set {
            var newValueCopy = newValue
            let objCType = NSValue(uiEdgeInsets: .zero).objCType
            let value = NSValue(&newValueCopy, withObjCType: objCType)
            objc_setAssociatedObject(self, &pTouchAreaEdgeInsets, value, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
        }
    }

    override open func point(inside point: CGPoint, with event: UIEvent?) -> Bool {
        if self.isHidden || !self.isEnabled || self.touchAreaEdgeInsets == .zero {
            return super.point(inside: point, with: event)
        }
        let newRect = self.bounds.inset(by: self.touchAreaEdgeInsets)
        return newRect.contains(point)
    }
}

按钮左对齐（左边图片，右边文字）：

class LeftAlignedIconButton: UIButton {
    override func titleRect(forContentRect contentRect: CGRect) -> CGRect {
        let titleRect = super.titleRect(forContentRect: contentRect)
        let imageSize = currentImage?.size ?? .zero
        let availableWidth = contentRect.width - imageEdgeInsets.right - imageSize.width - titleRect.width
        return titleRect.offsetBy(dx: round(availableWidth / 2), dy: 0)
    }
}

按钮状态的组合：

// https://www.jianshu.com/p/bd232eac8de8
button.setImage(image, for: UIControlState.selected.union(.highlighted))

UICollectionView​

实现一个左右滑动的轮播图，每张图的大小略小于屏幕宽度，显示第一张图时，第二张图能稍微露出一点点。

Many solutions presented here result in some weird behaviour that doesn't feel like properly implemented paging.

The solution presented in this tutorial, however, doesn't seem to have any issues. It just feels like a perfectly working paging algorithm. You can implement it in 5 simple steps:

Add the following property to your type: private var indexOfCellBeforeDragging = 0

Set the collectionView delegate like this: collectionView.delegate = self

Add conformance to UICollectionViewDelegate: YourType: UICollectionViewDelegate { }

Add the following method to the extension implementing the UICollectionViewDelegate conformance and set a value for pageWidth:

func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
    let pageWidth = // The width your page should have (plus a possible margin)
    let proportionalOffset = collectionView.contentOffset.x / pageWidth
    indexOfCellBeforeDragging = Int(round(proportionalOffset))
}

Add the following method to the extension implementing the UICollectionViewDelegate conformance, set the same value for pageWidth (you may also store this value at a central place) and set a value for collectionViewItemCount:

func scrollViewWillEndDragging(_ scrollView: UIScrollView, withVelocity velocity: CGPoint, targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    // Stop scrolling
    targetContentOffset.pointee = scrollView.contentOffset
    // Calculate conditions
    let pageWidth = // The width your page should have (plus a possible margin)
    let collectionViewItemCount = // The number of items in this section
    let proportionalOffset = collectionView.contentOffset.x / pageWidth
    let indexOfMajorCell = Int(round(proportionalOffset))
    let swipeVelocityThreshold: CGFloat = 0.5
    let hasEnoughVelocityToSlideToTheNextCell = indexOfCellBeforeDragging + 1 < collectionViewItemCount && velocity.x > swipeVelocityThreshold
    let hasEnoughVelocityToSlideToThePreviousCell = indexOfCellBeforeDragging - 1 >= 0 && velocity.x < -swipeVelocityThreshold
    let majorCellIsTheCellBeforeDragging = indexOfMajorCell == indexOfCellBeforeDragging
    let didUseSwipeToSkipCell = majorCellIsTheCellBeforeDragging && (hasEnoughVelocityToSlideToTheNextCell || hasEnoughVelocityToSlideToThePreviousCell)

    if didUseSwipeToSkipCell {
        // Animate so that swipe is just continued
        let snapToIndex = indexOfCellBeforeDragging + (hasEnoughVelocityToSlideToTheNextCell ? 1 : -1)
        let toValue = pageWidth * CGFloat(snapToIndex)
        UIView.animate(
            withDuration: 0.3,
            delay: 0,
            usingSpringWithDamping: 1,
            initialSpringVelocity: velocity.x,
            options: .allowUserInteraction,
            animations: {
                scrollView.contentOffset = CGPoint(x: toValue, y: 0)
                scrollView.layoutIfNeeded()
            },
            completion: nil
        )
    } else {
        // Pop back (against velocity)
        let indexPath = IndexPath(row: indexOfMajorCell, section: 0)
        collectionView.scrollToItem(at: indexPath, at: .left, animated: true)
    }
}

UIWindow​

新建项目后如何从代码中加载 ViewController 而不是 Storyboard？

class SceneDelegate: UIResponder, UIWindowSceneDelegate {
    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        guard let windowScene = (scene as? UIWindowScene) else { return }
        let window = UIWindow(windowScene: windowScene)
        let vc = ViewController()
        window.rootViewController = vc
        window.makeKeyAndVisible()
        self.window = window
    }
}

另外，删除 Info.plist 里面的两项有关 Storyboard 的键值。

UIView 截图​

extension UIView {
    func snapshot() -> UIImage {
        UIGraphicsBeginImageContextWithOptions(bounds.size, false, UIScreen.main.scale)
        drawHierarchy(in: bounds, afterScreenUpdates: true)
        let result = UIGraphicsGetImageFromCurrentImageContext()!
        UIGraphicsEndImageContext()
        return result
    }

    func renderAsImage() -> UIImage {
        let renderer = UIGraphicsImageRenderer(bounds: bounds)
        return renderer.image { rendererContext in
            layer.render(in: rendererContext.cgContext)
        }
    }
}

CALayer​

CAShapeLayer​

CAShapeLayer 画圆：

let circleView = UIView(frame: CGRect(x: 0, y: 0, width: 100, height: 100))
circleView.center = CGPoint(x: kMainScreenWidth/2, y: kMainScreenHeight*0.7)
let shapeLayer = CAShapeLayer()
let bezierPath = UIBezierPath(ovalIn: circleView!.bounds)
shapeLayer.path = bezierPath.cgPath
shapeLayer.strokeColor = UIColor.white.cgColor
shapeLayer.lineWidth = 5.0
shapeLayer.strokeStart = 0
shapeLayer.strokeEnd = 1
shapeLayer.fillColor = UIColor.clear.cgColor
circleView.layer.addSublayer(shapeLayer)
circleView.isUserInteractionEnabled = false
self.view.addSubview(circleView)

部分圆角：

let maskPath = UIBezierPath(roundedRect: normalView.bounds, byRoundingCorners: [UIRectCorner.topLeft, UIRectCorner.topRight], cornerRadii: CGSize(width: 10, height: 10))
let maskLayer = CAShapeLayer()
maskLayer.frame = normalView.bounds
maskLayer.path = maskPath.cgPath
normalView.layer.mask = maskLayer

CAGradientLayer​

从左到右渐变色，添加子图层方式：

let color1 = UIColor(rgba: "#F4DEA9")
let color2 = UIColor(rgba: "#F4C467")
let gradientColors: [CGColor] = [color1.cgColor, color2.cgColor]
let gradientLayer = CAGradientLayer()
gradientLayer.colors = gradientColors
gradientLayer.startPoint = CGPoint(x: 0, y: 0)
gradientLayer.endPoint = CGPoint(x: 1, y: 0)
gradientLayer.frame = unlockButton.bounds
button.layer.insertSublayer(gradientLayer, at: 0)

从左到右渐变色，UIView backing layer：

private class ProgressView: UIView {
    override class var layerClass: AnyClass { return CAGradientLayer.self }
}

let progressView = ProgressView()
let color1 = UIColor(rgba: "#15E78D")
let color2 = UIColor(rgba: "#BFF95D")
let gradientColors: [CGColor] = [color1.cgColor, color2.cgColor]
let gradientLayer = progressView.layer as! CAGradientLayer
gradientLayer.colors = gradientColors
gradientLayer.startPoint = CGPoint(x: 0, y: 0)
gradientLayer.endPoint = CGPoint(x: 1, y: 0)

UIImage​

图片模糊处理：

/// 图片模糊效果处理
/// - parameter image: 需要处理的图片
/// - parameter level: 模糊程度（0~1）
func blurry(_ image: UIImage, level: CGFloat) -> UIImage {

    // boxSize 必须大于 0
    let boxSize = level - level.truncatingRemainder(dividingBy: 2) + 1

    let _cgImage = image.cgImage

    // 图像缓存: 输入缓存、输出缓存
    var inBuffer = vImage_Buffer()
    var outBuffer = vImage_Buffer()
    var error = vImage_Error()

    let inProvider = _cgImage?.dataProvider
    let inBitmapData = inProvider?.data

    inBuffer.width = vImagePixelCount((_cgImage?.width)!)
    inBuffer.height = vImagePixelCount((_cgImage?.height)!)
    inBuffer.rowBytes = (_cgImage?.bytesPerRow)!
    inBuffer.data = UnsafeMutableRawPointer(mutating: CFDataGetBytePtr(inBitmapData!))

    // 像素缓存
    let pixelBuffer = malloc((_cgImage?.bytesPerRow)! * (_cgImage?.height)!)
    outBuffer.data = pixelBuffer
    outBuffer.width = vImagePixelCount((_cgImage?.width)!)
    outBuffer.height = vImagePixelCount((_cgImage?.height)!)
    outBuffer.rowBytes = (_cgImage?.bytesPerRow)!

    // 中间缓存区, 抗锯齿
    let pixelBuffer2 = malloc((_cgImage?.bytesPerRow)! * (_cgImage?.height)!)
    var outBuffer2 = vImage_Buffer()
    outBuffer2.data = pixelBuffer2
    outBuffer2.width = vImagePixelCount((_cgImage?.width)!)
    outBuffer2.height = vImagePixelCount((_cgImage?.height)!)
    outBuffer2.rowBytes = (_cgImage?.bytesPerRow)!

    error = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer2, nil, 0, 0, UInt32(boxSize), UInt32(boxSize), nil, vImage_Flags(kvImageEdgeExtend))
    error = vImageBoxConvolve_ARGB8888(&outBuffer2, &outBuffer, nil, 0, 0, UInt32(boxSize), UInt32(boxSize), nil, vImage_Flags(kvImageEdgeExtend))

    if error != kvImageNoError {
        debugPrint(error)
    }

    let colorSpace = CGColorSpaceCreateDeviceRGB()
    let ctx = CGContext(data: outBuffer.data, width: Int(outBuffer.width), height: Int(outBuffer.height), bitsPerComponent: 8, bytesPerRow: outBuffer.rowBytes, space: colorSpace, bitmapInfo: (_cgImage?.bitmapInfo.rawValue)!)

    let finalCGImage = ctx!.makeImage()
    let finalImage = UIImage(cgImage: finalCGImage!)

    free(pixelBuffer!)
    free(pixelBuffer2!)

    return finalImage
}

extension UIImage {
    func blurred(radius: CGFloat) -> UIImage {
        let ciContext = CIContext(options: nil)
        guard let cgImage = cgImage else { return self }
        let inputImage = CIImage(cgImage: cgImage)
        guard let ciFilter = CIFilter(name: "CIGaussianBlur") else { return self }
        ciFilter.setValue(inputImage, forKey: kCIInputImageKey)
        ciFilter.setValue(radius, forKey: kCIInputRadiusKey)
        guard let resultImage = ciFilter.value(forKey: kCIOutputImageKey) as? CIImage else { return self }
        guard let cgImage2 = ciContext.createCGImage(resultImage, from: inputImage.extent) else { return self }
        return UIImage(cgImage: cgImage2)
    }
}

extension UIImage {
    public func blur(size: Float) -> UIImage! {

        let boxSize = size - size.truncatingRemainder(dividingBy: 2) + 1

        guard let image = self.cgImage else { return nil }

        let height = vImagePixelCount(image.height)
        let width = vImagePixelCount(image.width)
        let bytesPerRow = image.bytesPerRow

        let inBitmapData = image.dataProvider!.data!
        let inData = UnsafeMutableRawPointer(mutating: CFDataGetBytePtr(inBitmapData))
        var inBuffer = vImage_Buffer(data: inData, height: height, width: width, rowBytes: bytesPerRow)

        let outData = malloc(bytesPerRow * Int(height))
        var outBuffer = vImage_Buffer(data: outData, height: height, width: width, rowBytes: bytesPerRow)

        let _ = vImageBoxConvolve_ARGB8888(&inBuffer, &outBuffer, nil, 0, 0, UInt32(boxSize), UInt32(boxSize), nil, vImage_Flags(kvImageEdgeExtend))

        let colorSpace = CGColorSpaceCreateDeviceRGB()
        let context = CGContext(data: outBuffer.data, width: Int(outBuffer.width), height: Int(outBuffer.height), bitsPerComponent: 8, bytesPerRow: outBuffer.rowBytes, space: colorSpace, bitmapInfo: image.bitmapInfo.rawValue)
        let imageRef = context!.makeImage()
        let bluredImage = UIImage(cgImage: imageRef!)

        free(outData)
        return bluredImage
    }
}

生成纯色图片：

extension UIImage {
    static func from(color: UIColor) -> UIImage {
        let rect = CGRect(x: 0, y: 0, width: 1, height: 1)
        UIGraphicsBeginImageContext(rect.size)
        let context = UIGraphicsGetCurrentContext()
        context!.setFillColor(color.cgColor)
        context!.fill(rect)
        let img = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return img!
    }
}

降采样：

    // data buffer - 图片从磁盘文件加载到内存中，这是经过编码的图片数据
    // image buffer - 图片解码后的数据，每个元素描述一个图片像素的颜色信息，buffer 的大小为 width*height*4 (rgba)
    // frame buffer - 类似于OpenGL的Frame Buffer，用于上传到GPU中成像

    // Downsampling large images for display at smaller size
    public class func downsample(imageAt imageURL: URL, to pointSize: CGSize, scale: CGFloat) -> UIImage? {
        // 设置`kCGImageSourceShouldCache`为`false`，可以避免缓存解码后的数据，64位设置上默认是开启缓存的
        let imageSourceOptions = [kCGImageSourceShouldCache: false] as CFDictionary
        if let imageSource = CGImageSourceCreateWithURL(imageURL as CFURL, imageSourceOptions) {
            return downsample(imageAt: imageSource, to: pointSize, scale: scale)
        } else {
            return nil
        }
    }

    public class func downsample(imageAt imageData: Data, to pointSize: CGSize, scale: CGFloat) -> UIImage? {
        let imageSourceOptions = [kCGImageSourceShouldCache: false] as CFDictionary
        if let imageSource = CGImageSourceCreateWithData(imageData as CFData, imageSourceOptions) {
            return downsample(imageAt: imageSource, to: pointSize, scale: scale)
        } else {
            return nil
        }
    }

    public class func downsample(imageAt imageSource: CGImageSource, to pointSize: CGSize, scale: CGFloat) -> UIImage? {
        let maxDimensionInPixels = max(pointSize.width, pointSize.height) * scale
        let downsampleOptions =
            [kCGImageSourceCreateThumbnailFromImageAlways: true,
             kCGImageSourceShouldCacheImmediately: true,
             kCGImageSourceCreateThumbnailWithTransform: true,
             kCGImageSourceThumbnailMaxPixelSize: maxDimensionInPixels] as CFDictionary
        if let downsampledImage =
            CGImageSourceCreateThumbnailAtIndex(imageSource, 0, downsampleOptions) {
            return UIImage(cgImage: downsampledImage)
        } else {
            return nil
        }
    }

生成渐变色图片：

func generateGradientImage(colors: [UIColor], imageSize: CGSize) -> UIImage? {
    let cgColors = colors.map{ $0.cgColor }
    let gradientLayer = CAGradientLayer()
    let frame = CGRect(origin: .zero, size: imageSize)
    gradientLayer.frame = frame
    gradientLayer.colors = cgColors
    gradientLayer.startPoint = CGPoint(x: 0.0, y: 0.5)
    gradientLayer.endPoint = CGPoint(x: 1.0, y: 0.5)

    UIGraphicsBeginImageContextWithOptions(gradientLayer.frame.size, gradientLayer.isOpaque, 0.0);

    guard let context = UIGraphicsGetCurrentContext() else { return nil }
    gradientLayer.render(in: context)
    let image = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return image
}

修改曝光值：

extension UIImage {
    func exposure(_ exposure: Float) -> UIImage {
        if let cgImage = self.cgImage {
            let context = CIContext()
            let ciImage = CIImage(cgImage: cgImage)
            let filter = CIFilter(name: "CIExposureAdjust")
            filter?.setValue(ciImage, forKey: kCIInputImageKey)
            filter?.setValue(exposure, forKey: kCIInputEVKey)
            if let outputImage = filter?.outputImage, let imageRef = context.createCGImage(outputImage, from: ciImage.extent) {
                let uiImage = UIImage(cgImage: imageRef)
                return uiImage
            }
        }
        return self
    }
}

UIColor​

hex 颜色：

extension UIColor {
    public convenience init(hex: Int) {
        let red: CGFloat = CGFloat((hex >> 16) & 0x0000FF) / 255.0
        let green: CGFloat = CGFloat((hex >> 8) & 0x0000FF) / 255.0
        let blue: CGFloat = CGFloat(hex & 0x0000FF) / 255.0
        self.init(red:red, green:green, blue:blue, alpha:1.0)
    }
}

Media Player​

Becoming a Now Playable App

页面时长统计打点​

private var viewDidAppearDate = Date()

override func viewDidLoad() {
    super.viewDidLoad()

    NotificationCenter.default.addObserver(self, selector: #selector(appDidBecomeActive(_:)), name: UIApplication.didBecomeActiveNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(appWillResignActive(_:)), name: UIApplication.willResignActiveNotification, object: nil)
}

override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    viewDidAppearDate = Date()
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    let duration = Date().timeIntervalSince(self.viewDidAppearDate)
    if duration < 100000 {
        log(duration)
    }
}

@objc func appDidBecomeActive(_ notification: Any) {
    viewDidAppearDate = Date()
}

@objc func appWillResignActive(_ notification: Any) {
    let duration = Date().timeIntervalSince(self.viewDidAppearDate)
    if duration < 100000 {
        log(duration)
    }
}