弱引用、强引用

• OC

__weak typeof(self) weakSelf = self 
__strong typeof(weakSelf) strongSelf = weakSelf  // 用于弱引用可能在闭包中销毁self的情况

• Swift

[weak self]
guard let strongSelf = self else { return } // 用于弱引用可能在闭包中销毁self的情况

懒加载

• OC

-(UILabel*)nickLabel {
  if(nickLabel == nil) {
    UILabel *nick = [[UILabel alloc] init];
  }
  return nick;
}

• Swift

lazy var nickLabel: UILabel = {
  let nick = UILabel()
  return nick
}()