PS：Xcode 版本是 Version 9.2 (9C40b)，编译 Swift 版本是：3.2

NSObject+ClassName

功能：获取某个对象或者某个类的类名字符串（比如 xib 加载）

extension NSObject {
    
    /// 返回类名字符串
    static var className: String {
        return String(describing: self)
    }
    
    /// 返回类名字符串
    var className: String {
        return String(describing: type(of: self))
    }
}

String+BoundingRect

功能：计算字符串在 label 上的宽高（比如 cell 自适应高度）

extension String {

    /// 给定最大宽计算高度，传入字体、行距、对齐方式（便捷调用）
    func heightForLabel(width: CGFloat, font: UIFont, lineSpacing: CGFloat = 5, alignment: NSTextAlignment = .left) -> CGFloat {
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.lineSpacing = lineSpacing
        paragraphStyle.alignment = alignment
        let attributes: [String : Any] = [
            NSFontAttributeName: font,
            NSParagraphStyleAttributeName: paragraphStyle
        ]
        let textSize = textSizeForLabel(width: width, height: CGFloat(Float.greatestFiniteMagnitude), attributes: attributes)
        return textSize.height
    }
    
    /// 给定最大宽计算高度，传入属性字典（便捷调用）
    func heightForLabel(width: CGFloat, attributes: [String: Any]) -> CGFloat {
        let textSize = textSizeForLabel(width: width, height: CGFloat(Float.greatestFiniteMagnitude), attributes: attributes)
        return textSize.height
    }
    
    /// 给定最大高计算宽度，传入字体（便捷调用）
    func widthForLabel(height: CGFloat, font: UIFont) -> CGFloat {
        let labelTextAttributes = [NSFontAttributeName: font]
        let textSize = textSizeForLabel(width: CGFloat(Float.greatestFiniteMagnitude), height: height, attributes: labelTextAttributes)
        return textSize.width
    }
    
    /// 给定最大高计算宽度，传入属性字典（便捷调用）
    func widthForLabel(height: CGFloat, attributes: [String: Any]) -> CGFloat {
        let textSize = textSizeForLabel(width: CGFloat(Float.greatestFiniteMagnitude), height: height, attributes: attributes)
        return textSize.width
    }
    
    /// 给定最大宽高计算宽度和高度，传入字体、行距、对齐方式（便捷调用）
    func textSizeForLabel(width: CGFloat, height: CGFloat, font: UIFont, lineSpacing: CGFloat = 5, alignment: NSTextAlignment = .left) -> CGSize {
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.lineSpacing = lineSpacing
        paragraphStyle.alignment = alignment
        let attributes: [String : Any] = [
            NSFontAttributeName: font,
            NSParagraphStyleAttributeName: paragraphStyle
        ]
        let textSize = textSizeForLabel(width: width, height: height, attributes: attributes)
        return textSize
    }
    
    /// 给定最大宽高计算宽度和高度，传入属性字典（便捷调用）
    func textSizeForLabel(size: CGSize, attributes: [String: Any]) -> CGSize {
        let textSize = textSizeForLabel(width: size.width, height: size.height, attributes: attributes)
        return textSize
    }
    
    /// 给定最大宽高计算宽度和高度，传入属性字典（核心)
    func textSizeForLabel(width: CGFloat, height: CGFloat, attributes: [String: Any]) -> CGSize {
        let defaultOptions: NSStringDrawingOptions = [.usesLineFragmentOrigin, .usesFontLeading]
        let maxSize = CGSize(width: width, height: height)
        let rect = self.boundingRect(with: maxSize, options: defaultOptions, attributes: attributes, context: nil)
        let textWidth: CGFloat = CGFloat(Int(rect.width) + 1)
        let textHeight: CGFloat = CGFloat(Int(rect.height) + 1)
        return CGSize(width: textWidth, height: textHeight)
    }
}

extension NSAttributedString {
    
    /// 根据最大宽计算高度（便捷调用)
    func heightForLabel(width: CGFloat) -> CGFloat {
        let textSize = textSizeForLabel(width: width, height: CGFloat(Float.greatestFiniteMagnitude))
        return textSize.height
    }
    
    /// 根据最大高计算宽度（便捷调用)
    func widthForLabel(height: CGFloat) -> CGFloat {
        let textSize = textSizeForLabel(width: CGFloat(Float.greatestFiniteMagnitude), height: height)
        return textSize.width
    }
    
    /// 计算宽度和高度（核心)
    func textSizeForLabel(width: CGFloat, height: CGFloat) -> CGSize {
        let defaultOptions: NSStringDrawingOptions = [.usesLineFragmentOrigin, .usesFontLeading]
        let maxSize = CGSize(width: width, height: height)
        let rect = self.boundingRect(with: maxSize, options: defaultOptions, context: nil)
        let textWidth: CGFloat = CGFloat(Int(rect.width) + 1)
        let textHeight: CGFloat = CGFloat(Int(rect.height) + 1)
        return CGSize(width: textWidth, height: textHeight)
    }
}

String+RegularExpression

功能：主要是简化和统一外部使用正则表达式

extension String {
    /// 通过正则表达式匹配替换
    func replacingStringOfRegularExpression(pattern: String, template: String) -> String {
        var content = self
        do {
            let range = NSRange(location: 0, length: content.count)
            let expression = try NSRegularExpression(pattern: pattern, options: .caseInsensitive)
            content = expression.stringByReplacingMatches(in: content, options: .reportCompletion, range: range, withTemplate: template)
        } catch {
            print("regular expression error")
        }
        return content
    }
    
    /// 通过正则表达式匹配返回结果
    func matches(pattern: String) -> [NSTextCheckingResult] {
        do {
            let range = NSRange(location: 0, length: count)
            let expression = try NSRegularExpression(pattern: pattern, options: .caseInsensitive)
            let matchResults = expression.matches(in: self, options: .reportCompletion, range: range)
            return matchResults
        } catch {
            print("regular expression error")
        }
        return []
    }
    
    /// 通过正则表达式返回第一个匹配结果
    func firstMatch(pattern: String) -> NSTextCheckingResult? {
        do {
            let range = NSRange(location: 0, length: count)
            let expression = try NSRegularExpression(pattern: pattern, options: .caseInsensitive)
            let match = expression.firstMatch(in: self, options: .reportCompletion, range: range)
            return match
            
        } catch {
            print("regular expression error")
        }
        return nil
    }
}

String+Substr

功能：字符串截取快捷方法，你懂的(⊙o⊙)…

extension String {
    
    ///  寻找在 startString 和 endString 之间的字符串
    func substring(between startString: String, and endString: String?, options: String.CompareOptions = .caseInsensitive) -> String? {
        let range = self.range(of: startString, options: options)
        if let startIndex = range?.upperBound {
            let string = self.substring(from: startIndex)
            if let endString = endString {
                let range = string.range(of: endString, options: options)
                if let startIndex = range?.lowerBound {
                    return string.substring(to: startIndex)
                }
            }
            return string
        }
        return nil
    }
    
    ///  寻找 prefix 字符串，并返回从 prefix 到尾部的字符串
    func substring(prefix: String, options: String.CompareOptions = .caseInsensitive, isContain: Bool = true) -> String? {
        let range = self.range(of: prefix, options: options)
        if let startIndex = range?.upperBound {
            var resultString = self.substring(from: startIndex)
            if isContain {
                resultString = "\(prefix)\(resultString)"
            }
            return resultString
        }
        return nil
    }
    
    ///  寻找 suffix 字符串，并返回从头部到 suffix 位置的字符串
    func substring(suffix: String, options: String.CompareOptions = .caseInsensitive, isContain: Bool = false) -> String? {
        let range = self.range(of: suffix, options: options)
        if let startIndex = range?.lowerBound {
            var resultString = self.substring(to: startIndex)
            if isContain {
                resultString = "\(resultString)\(suffix)"
            }
            return resultString
        }
        return nil
    }
    
    ///  从 N 位置到尾位置的字符串
    func substring(from: IndexDistance) -> String? {
        let index = self.index(self.startIndex, offsetBy: from)
        return self.substring(from: index)
    }
    
    ///  从头位置到 N 位置的字符串
    func substring(to: IndexDistance) -> String? {
        let index = self.index(self.startIndex, offsetBy: to)
        return self.substring(to: index)
    }
    
    /// 以 lower 为起点，偏移 range 得到的字符串
    func substring(_ lower: IndexDistance, _ range: IndexDistance) -> String? {
        let lowerIndex = self.index(self.startIndex, offsetBy: lower)
        let upperIndex = self.index(lowerIndex, offsetBy: range)
        let range = Range(uncheckedBounds: (lowerIndex, upperIndex))
        return self.substring(with: range)
    }
}

UIFont+Convenience

功能：除了简化自定义字体的引入外，这里可以统一管理字体大小，比如对字体大小进行统一屏幕适配

enum FontWeight: String {
    case light = "Light"
    case regular = "Regular"
    case medium = "Medium"
    case semibold = "Semibold"
    case bold = "Bold"
    case heavy = "Heavy"
}

enum FontType: String {
    case PingFangSC = "PingFangSC"
    case SFProText = "SFProText"
}

extension UIFont {
    
    static func heavyFont(ofSize fontSize: CGFloat, type: FontType = .PingFangSC) -> UIFont {
        return customFont(type, weight: .heavy, fontSize: fontSize)
    }
    
    static func regularFont(ofSize fontSize: CGFloat, type: FontType = .PingFangSC) -> UIFont {
        return customFont(type, weight: .regular, fontSize: fontSize)
    }
    
    static func boldFont(ofSize fontSize: CGFloat, type: FontType = .PingFangSC) -> UIFont {
        return customFont(type, weight: .bold, fontSize: fontSize)
    }
    
    static func lightFont(ofSize fontSize: CGFloat, type: FontType = .PingFangSC) -> UIFont {
        return customFont(type, weight: .light, fontSize: fontSize)
    }
    
    static func mediumFont(ofSize fontSize: CGFloat, type: FontType = .PingFangSC) -> UIFont {
        return customFont(type, weight: .medium, fontSize: fontSize)
    }
    
    static func semiboldFont(ofSize fontSize: CGFloat, type: FontType = .PingFangSC) -> UIFont {
        return customFont(type, weight: .semibold, fontSize: fontSize)
    }
    
    /// 自定义字体
    static func customFont(_ type: FontType, weight: FontWeight, fontSize: CGFloat) -> UIFont {
        let realFontSize = fontSize
        if let customFont = UIFont(name: "\(type.rawValue)-\(weight.rawValue)", size: realFontSize) {
            return customFont
        }
        if #available(iOS 8.2, *) {
            var systemWeight: CGFloat = UIFontWeightRegular
            switch weight {
            case .light:
                systemWeight = UIFontWeightLight
            case .regular:
                systemWeight = UIFontWeightRegular
            case .medium:
                systemWeight = UIFontWeightMedium
            case .semibold:
                systemWeight = UIFontWeightSemibold
            case .bold:
                systemWeight = UIFontWeightBold
            case .heavy:
                systemWeight = UIFontWeightHeavy
            }
            return UIFont.systemFont(ofSize: realFontSize, weight: systemWeight)
        } else {
            return UIFont.systemFont(ofSize: realFontSize)
        }
    }
}

UIView+Convenience

功能：一些常用的视图操作，比如 xib 加载、截图、找响应控制器

extension UIView {
    
    /// 从 xib 中加载视图
    func loadViewFromNib(index: Int = 0) -> UIView? {
        let classInstance = type(of: self)
        let nibName = classInstance.className
        let nib = UINib(nibName: nibName, bundle: nil)
        
        if let views = nib.instantiate(withOwner: self, options: nil) as? [UIView] {
            return views.safeIndex(index)
        }
        return nil
    }

    /// 寻找当前视图所在的控制器
    var responderController: UIViewController? {
        var nextReponder: UIResponder? = self.next
        while nextReponder != nil {
            if let viewController = nextReponder as? UIViewController {
                return viewController
            }
            nextReponder = nextReponder?.next
        }
        return nil
    }

    /// 生成视图的截图
    func displayViewToImage() -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(self.bounds.size, false, 0)
        if let context = UIGraphicsGetCurrentContext() {
            self.layer.render(in: context)
        }
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return image
    }

}

CollectionView+Convenience

功能：主要是为了简化 CollectionView 注册和从缓冲池取控件的代码

extension UICollectionView {
    
    /// 批量注册 Cell
    func registerForCells<T: UICollectionReusableView>(_ cellClasses: [T.Type], isNib: Bool = true) {
        cellClasses.forEach { cellClass in
            registerForCell(cellClass, isNib: isNib)
        }
    }
    
    /// 注册 Cell
    func registerForCell<T: UICollectionReusableView>(_ cellClass: T.Type, identifier: String? = nil, isNib: Bool = true) {
        let nibName = cellClass.className
        let cellIdentifier = identifier ?? nibName
        if isNib {
            self.register(UINib(nibName: nibName, bundle: nil), forCellWithReuseIdentifier: cellIdentifier)
        } else {
            self.register(cellClass, forCellWithReuseIdentifier: cellIdentifier)
        }
    }
    
    /// 注册顶部视图
    func registerForHeader<T: UICollectionReusableView>(_ cellClass: T.Type, identifier: String? = nil, isNib: Bool = true) {
        let nibName = cellClass.className
        let headerIdentifier = identifier ?? nibName
        if isNib {
            self.register(UINib(nibName: nibName, bundle: nil), forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: headerIdentifier)
        } else {
            self.register(cellClass, forSupplementaryViewOfKind: UICollectionElementKindSectionHeader, withReuseIdentifier: headerIdentifier)
        }
    }
    
    /// 注册底部视图
    func registerForFooter<T: UICollectionReusableView>(_ cellClass: T.Type, identifier: String? = nil, isNib: Bool = true) {
        let nibName = cellClass.className
        let footerIdentifier = identifier ?? nibName
        if isNib {
            self.register(UINib(nibName: nibName, bundle: nil), forSupplementaryViewOfKind: UICollectionElementKindSectionFooter, withReuseIdentifier: footerIdentifier)
        } else {
            self.register(cellClass, forSupplementaryViewOfKind: UICollectionElementKindSectionFooter, withReuseIdentifier: footerIdentifier)
        }
    }
    
    /// 从缓存池取出 Cell
    func dequeueCell<T: UICollectionReusableView>(_ cellClass: T.Type, reuseIdentifier: String? = nil, indexPath: IndexPath) -> T {
        let identifier: String = reuseIdentifier ?? cellClass.className
        if let cell = dequeueReusableCell(withReuseIdentifier: identifier, for: indexPath) as? T {
            return cell
        } else {
            return T()
        }
    }
    
    /// 从缓存池取出顶部或者底部实体
    func dequeueSupplementaryView<T: UICollectionReusableView>(_ viewClass: T.Type, kind: String, indexPath: IndexPath) -> T {
        let identifier = viewClass.className
        if let cell = dequeueReusableSupplementaryView(ofKind: kind, withReuseIdentifier: identifier, for: indexPath) as? T {
            return cell
        } else {
            return T()
        }
    }
    
    /// 滑动到第一个 Cell 位置，通过增加判断，防止奔溃
    func scrollToFirstCell(animated: Bool = true) {
        guard self.numberOfSections > 0 else { return }
        guard let count = self.dataSource?.collectionView(self, numberOfItemsInSection: 0) else { return }
        if count > 0 {
            if let flowLayout = self.collectionViewLayout as? UICollectionViewFlowLayout {
                if flowLayout.scrollDirection == .horizontal {
                    scrollToItem(at: IndexPath(row: 0, section: 0), at: .left, animated: animated)
                } else {
                    scrollToItem(at: IndexPath(row: 0, section: 0), at: .top, animated: animated)
                }
            }
        }
    }
}

Array+Convenience

功能：数组便捷操作，其中 safeIndex 是为了防止数组越界，双边遍历的需求是为了优化显示图片列表加载，从用户当前看到的图片开始向两边加载

extension Array {
    
    /// 获取数组中的元素，增加了数组越界的判断
    func safeIndex(_ i: Int) -> Array.Iterator.Element? {
        guard !isEmpty && self.count > abs(i) else {
            return nil
        }
        
        for item in self.enumerated() {
            if item.offset == I {
                return item.element
            }
        }
        return nil
    }
    
    /// 从前面取 N 个数组元素
    func limit(_ limitCount: Int) -> [Array.Iterator.Element] {
        let maxCount = self.count
        var resultCount: Int = limitCount
        if maxCount < limitCount {
            resultCount = maxCount
        }
        if resultCount <= 0 {
            return []
        }
        return self[0..<resultCount].map { $0 }
    }
    
    /// 填充数组数量到 N
    func full(_ fullCount: Int) -> [Array.Iterator.Element] {
        var items = self
        while items.count > 0 && items.count < fullCount {
            items = (items + items).limit(fullCount)
        }
        return items.limit(fullCount)
    }
    
    /// 双边遍历，从中间向两边进行遍历
    func bilateralEnumerated(_ beginIndex: Int, handler: (Int, Array.Iterator.Element) -> Void) {
        let arrayCount: Int = self.count
        var leftIndex: Int = Swift.max(0, Swift.min(beginIndex, arrayCount - 1))
        var rightIndex: Int = leftIndex + 1
        var currentIndex: Int = leftIndex
        var isLeftEnable: Bool = leftIndex >= 0 && leftIndex < arrayCount
        var isRightEnable: Bool = rightIndex >= 0 && rightIndex < arrayCount
        var isLeft: Bool = isLeftEnable ? true : isRightEnable
        while isLeftEnable || isRightEnable {
            currentIndex = isLeft ? leftIndex : rightIndex
            if let element = self.safeIndex(currentIndex) {
                handler(currentIndex, element)
            }
            if isLeft {
                leftIndex -= 1
            } else {
                rightIndex += 1
            }
            isLeftEnable = leftIndex >= 0 && leftIndex < arrayCount
            isRightEnable = rightIndex >= 0 && rightIndex < arrayCount
            if isLeftEnable && !isRightEnable {
                isLeft = true
            } else  if !isLeftEnable && isRightEnable {
                isLeft = false
            } else if isLeftEnable && isRightEnable {
                isLeft = !isLeft
            }
        }
    }
}

NSDictionary+Convenience

功能：简化从字典中取值的代码，并支持多键查找

extension NSDictionary {
    
    // MARK: - 以下都是从字典里取值的快捷方法，支持多键查找和默认返回
    func bool(_ keys: String..., defaultValue: Bool = false) -> Bool {
        return valueForKeys(keys, type: Bool.self) ?? defaultValue
    }
    
    func double(_ keys: String..., defaultValue: Double = 0.0) -> Double {
        return valueForKeys(keys, type: Double.self) ?? defaultValue
    }
    
    func int(_ keys: String..., defaultValue: Int = 0) -> Int {
        return valueForKeys(keys, type: Int.self) ?? defaultValue
    }
    
    func string(_ keys: String..., defaultValue: String? = nil) -> String? {
        return valueForKeys(keys, type: String.self) ?? defaultValue
    }
    
    func dictionary(_ keys: String..., defaultValue: NSDictionary? = nil) -> NSDictionary? {
        return valueForKeys(keys, type: NSDictionary.self) ?? defaultValue
    }
    
    func array<T>(_ keys: String..., type: T.Type, defaultValue: [T] = []) -> [T] {
        return valueForKeys(keys, type: Array<T>.self) ?? defaultValue
    }
    
    // MARK: - 以下是从字典里取值的核心方法，支持多键查找
    fileprivate func valueForKeys<T>(_ keys: [String], type: T.Type) -> T? {
        for key in keys {
            if let result = self[key] as? T {
                return result
            }
        }
        return nil
    }
}

Demo 源代码在这：02-CommonExtensionDemo

这些分类方法都是我在项目中比较常用的，能简化很多代码，希望你们喜欢！O(∩_∩)O哈哈~