预览提供者-PreviewProvider
一个在Xcode中产生视图预览的类型。
A type that produces view previews in Xcode.
说明-Declaration
protocol PreviewProvider : _PreviewProvide
概述-Overview
Xcode静态地在你的应用程序中发现符合PreviewProvider协议的类型，并为它发现的每个提供者生成预览。
Xcode statically discovers types that conform to the
PreviewProviderprotocol in your app, and generates previews for each provider it discovers.