In case of Android when I want to send or attach a document such as a pdf or doc from my application I can easily access all the files in the external storage and share or attach.
But since iOS follows a sandbox approach as well as there is no filesystem so it is not possible to attach or upload in same manner.
In my iOS application right now, I have implemented Open In functionality, wherein in the info.plist file I have specified that my application supports all types of documents so when the user opens any documents he gets an option to Open In my application, then I save that document in the
Documents/Incoming
folder in the application, now when my user clicks to add attachment then he can see the document to attach, since this is a long process I was looking for better ones.
I saw whatsApp allows uploading/sharing from iCloud apart from that what can I do to provide a similar behaviour as Android.