Swift 编程和 OC 编程区别小记

1. edgesForExtendedLayout 设置为 None

• OC

  self.edgesForExtendedLayout = UIRectEdgeNone;
  

• Swift

  // Swift 没有 None 选项，通过初始化设置
  self.edgesForExtendedLayout = UIRectEdge.init(rawValue: 0)
  或
  edgesForExtendedLayout = UIRectEdge.init(rawValue: 0)    // 编码规范(风格)区别
  

由于导航栏是半透明的，设置为 None 时会显示黑色，需要设置self.navigationController.navigationBar.translucent = NO; 或navigationController?.navigationBar.isTranslucent = false

2. 自定义 UIView 底层支持图层（CALayer），这里以设置为 AVPlayerLayer 为例

• OC

  // 重写类方法
  + (Class)layerClass {
      return [AVPlayerLayer class]
  }
  // 在需要的地方设置图层的相关的属性，avPlayer = AVPlayer()
  [(AVPlayerLayer *)[self layer] setPlayer:avPlayer];
  

• Swift

  override class var layerClass: AnyClass  {
     get {
         return AVPlayerLayer.self
     }
  }
  // 设置属性
  guard let avPlayerLayer = self.layer as? AVPlayerLayer else {
      return
  }
  avPlayerLayer.player = avPlayer
  

3. 通过类名字符串初始化对象，以 HomeViewController 为例

• OC

  NSString *className = @"HomeViewController";
  HomeViewController *homeViewController = [[NSClassFromString(className) alloc] init];
  

• Swift

  let classString = "HomeViewController"
  let className = Bundle.main.infoDictionary!["CFBundleName"] as! String + "." + classString // 这里项目名不能带有下划线 “_” 或 “*” 等特殊字符
  let viewControllerClass = NSClassFromString(className) as! UIViewController.Type
  let homeViewController  = viewControllerClass.init()
  

4. 单例模式实现

• OC

  static Singleton* _instance = nil;  
  + (instancetype) shareInstance {  
      static dispatch_once_t onceToken ;  
      dispatch_once(&onceToken, ^{  
      _instance = [[self alloc] init] ;  
      }) ;   
     return _instance ;  
  } 
  

• Swift

  final class Singleton {
     private init() { }
     static let shared = Singleton()
  }
  

5. 获取字典中的键、值

• OC

  NSDictionary *dictionary = [@"key": @"value"];
  NSArray *keys = dictionary.allKeys;
  

• Swift

  let dictionary = ["key": "value"]
  let keys = Array(dictionary.keys)  // 这里 dictionary.keys 不再是数组，需要再转换
  

未完待续，欢迎补充