ScrollView Zoom

1.加入ScrollViewDelegate

2.設定ScrollView的Delegate為UIImageViewController

scrowView.delegate = self

3.設置zomm的方法 要放大縮小的物件為 imageView

 func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        return imageView
    }

4.設定最大最小放大值

 scrowView.maximumZoomScale = 2.0
 scrowView.minimumZoomScale = 0.1

為UIViewController 加入 extention

為了讓ipad版本SplitViewController有個Tittle
所以加了一個NavigationViewController在前面

但這樣直接跑會有問題segues的終點就不是UIImageViewController了
所以我們為UiViewController加入一個擴充屬性
如果自己是NavigationController的話 回傳他下一個可見的ViewController
沒有的話回傳自己

extension UIViewController {
    var contentViewController: UIViewController{
        if let navcon = self as? UINavigationController{
            return navcon.visibleViewController ?? self
        }else {
            return self
        }
    }
}

這樣prepare segues就不會有問題

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        if segue.identifier == Storyboard.ShowImageSegues {
            //這裡就直接取contentViewController
           if let imc = segue.destination.contentViewController as? ImageViewController{
                let imageName = (sender as? UIButton)?.currentTitle!
                imc.ImageURL = DemoURL.NASAImageName(imageName: imageName)
                imc.title = imageName
            }
        }
    }