The new CaseIterable protocol gives your Enum new ability to generate an array of all cases in an enum.

The error message when you reused an AVCapturePhotoSettings object is -[AVCapturePhotoOutput capturePhotoWithSettings:delegate:] Settings may not be re-used'.

直接跳到Swift语言吧。Swift很快很安全，而且就我的感受来说，写Swift有一种写脚本语言的快感。但是Swift还有很多路要走，现在最感到头疼的就是和ObjC的混编吧。

更多数据结构

数据结构

AVPlayer

AVFoundation provides a controller class AVPlayer to play timed audio-visual media. The AVPlayer can handle playback of local, progressively downloaded and streamed media conforming HLS protocol.

AVAsset is an abstract, immutable class providing a composite representation of a media resource, modeling the static attributes of the media as a whole, such as its title, duration, and metadata. AVAsset is not the media itself, but acts as a container for timed media. It is composed of one or more media tracks along with metadata describing its contents.