Swift startAccessingSecurityScopedResource（）返回始终为false

当我尝试从iCloud驱动器或Dropbox将文件导入服务器时，startAccessingSecurityScopedResource仅返回false设备，但在模拟器Xcode 8、Swift 2.3、最小目标8.0中测试时返回true

这是我的代码：

{
        func showCloudDriveAction(inputBar: NAChatInputBar) {
           let documentmenuPicker = UIDocumentMenuViewController(documentTypes: ["public.data"], inMode: .Import)
           documentmenuPicker.delegate = self
           presentViewController?.presentViewController(documentmenuPicker, animated: true, completion: nil)
       }

}

extension NAChatInputBarPresenter: UIDocumentPickerDelegate, UIDocumentMenuDelegate {

    public func documentMenu(documentMenu: UIDocumentMenuViewController, didPickDocumentPicker documentPicker: UIDocumentPickerViewController) {
        documentPicker.delegate = self
        self.presentViewController?.presentViewController(documentPicker, animated: true, completion: nil)
    }

    public func documentPicker(controller: UIDocumentPickerViewController, didPickDocumentAtURL url: NSURL) {
        if url.startAccessingSecurityScopedResource() {
            guard let path = url.path, data = NSData(contentsOfFile: path) else {
                return
            }
            delegate?.chatInputBarPresenter(data, atUrl: url)
            url.stopAccessingSecurityScopedResource()
        }
    }

}

startAccessingSecurityScopedResource不必返回true，只需与stopAccessingSecurityScopedResource配对即可

如果返回false，您仍然可以使用NSFileCoordinator访问资源

let isSecuredURL = url.startAccessingSecurityScopedResource() == true
let coordinator = NSFileCoordinator()
var error: NSError? = nil
coordinator.coordinate(readingItemAt: url, options: [], error: &error) { (url) -> Void in
    do {
        // do something
    } catch (_) {
        // something went wrong
    }
}
if (isSecuredURL) {
    url.stopAccessingSecurityScopedResource()
}

我猜如果ISSecureURL{url.stopAccessingSecurityScopedResource}应该在catch块之后，在闭包内部