1     // MARK:- 重写构造函数
 2     override init(frame: CGRect) {
 3         super.init(frame: frame)
 4        
 5         setupUI()
 6     }
 7     // required : 如果一个构造函数前有required,那么重写了其他构造函数时,那么该构造函数也必须被重写
 8     required init?(coder aDecoder: NSCoder) {
 9         fatalError("init(coder:) has not been implemented")
10     }

1    // 2.获取小图片
2             var smallImage = SDWebImageManager.sharedManager().imageCache.imageFromDiskCacheForKey(shop.q_pic_url)
3             if smallImage == nil {
4                 smallImage = UIImage(named: "empty_picture")
5             }

collectionView.scrollToItemAtIndexPath(indexPath!, atScrollPosition: .CenteredHorizontally, animated: false)

1 // ?? : 先判断前面的可选链是否有值, 如果有值,解包并且获取对应类型的值. 如果没有值直接取后面的值
2         return shops?.count ?? 0

1  // 1.1.拿到正在显示的Cell
2         // visibleCells 返回所有在屏幕中显示的Cell
3         let cell = collectionView.visibleCells()[0] as! PhotoBrowserViewCell
4         guard let image = cell.imageView.image else {
5             return
6         }

 1 // MARK:- 遵守转场的代理协议,和实现对应的方法
 2 extension HomeViewController : UIViewControllerTransitioningDelegate {
 3     // 为弹出控制器做一个动画
 4     func animationControllerForPresentedController(presented: UIViewController, presentingController presenting: UIViewController, sourceController source: UIViewController) -> UIViewControllerAnimatedTransitioning? {
 5      //记录当前为显示阶段
 6      isPresented = true
 7         return self
 8     }
 9   
10     // 为消失控制器做一个动画
11     func animationControllerForDismissedController(dismissed: UIViewController) -> UIViewControllerAnimatedTransitioning? {
12       //记录当前为消失阶段
13       isPresented = false
14         return self
15     }
16 }
17  
18 extension HomeViewController : UIViewControllerAnimatedTransitioning {
19     // 返回动画执行的时间
20     func transitionDuration(transitionContext: UIViewControllerContextTransitioning?) -> NSTimeInterval {
21         return 3
22     }
23    
24     // transitionContext : 转场上下文
25     // 作用 : 可以通过上下文获取到弹出的View和消失的View
26     // UITransitionContextFromViewKey : 获取消失的View
27     // UITransitionContextToViewKey : 获取弹出的View
28     func animateTransition(transitionContext: UIViewControllerContextTransitioning) {
29         if isPresented {
30             // 获取弹出的View
31             let presentedView = transitionContext.viewForKey(UITransitionContextToViewKey)!
32            //需要把view添加到父控件上,才能有动画效果  
33           //父控件就是widow的containerView,    通过transitionContext.containerView()拿到
34             transitionContext.containerView()?.addSubview(presentedView)
35            
36             // 修改View alpha值
37             presentedView.alpha = 0.0
38            
39             // 执行动画
40             UIView.animateWithDuration(transitionDuration(transitionContext), animations: {
41                 presentedView.alpha = 1.0
42             }) { (isFinished : Bool) in
43                //告诉控制器,转场动画完成
44                 transitionContext.completeTransition(isFinished)
45             }
46         } else {
47             // 1.获取消失的View
48             let dismissedView = transitionContext.viewForKey(UITransitionContextFromViewKey)!
49            
50             // 2.执行动画
51             UIView.animateWithDuration(transitionDuration(transitionContext), animations: {
52                 dismissedView.alpha = 0.0
53                 }, completion: { (isFinished : Bool) in
54                     //移除view,显示主控制器的view
55                     dismissedView.removeFromSuperview()
56                     transitionContext.completeTransition(isFinished)
57             })
58         }
59     }
60 }