iOS获取收藏夹带有sortDeScriptor设置为localidentifier

Question

看来我无法得到由localidentifier排序的提取结果。这是代码：

let sortDescriptor = NSSortDescriptor(key: "localIdentifier", ascending: true)
let options = PHFetchOptions()
options.sortDescriptors = [sortDescriptor]
let albums = PHCollection.fetchTopLevelUserCollections(with: options)
print(albums.count)

我有一个错误：

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Unsupported sort descriptor in fetch options: (localIdentifier, ascending, compare:)'

但是，在Apple Doc中，LocalIdentifier可以用作密钥。

Answer 1

，因为对象phcollection没有这样的键" localidentifier"。使用key＆quot" entainizedTitle"，他是作品

let sortDescriptor = NSSortDescriptor(key: "localizedTitle", ascending: true)