一些老的初始化方法發(fā)現(xiàn)在iOS14已經(jīng)棄用巩梢，例如
init(documentTypes allowedUTIs: [String], in mode: UIDocumentPickerMode)
init(url: URL, in mode: UIDocumentPickerMode)
init(urls: [URL], in mode: UIDocumentPickerMode)
一些新的方法iOS14之后使用的發(fā)現(xiàn)在代碼中根本索引不出來，例如
init(forOpeningContentTypes contentTypes: [UTType], asCopy: Bool)
convenience init(forOpeningContentTypes contentTypes: [UTType])
此時需要引入頭文件
import UniformTypeIdentifiers
