iOS UIDocumentBrowserViewController获取所选文件的URL路径

I am working on an iOS plugin for an unity project and for that i need to give user the possibility to browse the files on the device and pick a zip file.I need to pass the url path of the selected file or copy it to the local sandbox(if possible).For this i've used UIDocumentBrowserViewController where i've managed to make the interface for user to select the desired file.The problem is that i don't really get what's happening even though i've spent hours and hours on the Apple documentation.I am working on an iOS plugin for an unity proj