I am writing an iOS application that performs conversion of a file saved by another application on the same device to another format. How can I transfer files from one appli
UIDocumentInteractionController is your friend.
Basically it works like this:
UIDocumentInteractionController and will give users the options to "send the file to App1" (I believe this has to be user activated)-(BOOL)application:openURL:sourceApplication:annotation: and deals with the transferred file which will be saved in your Documents/Inbox directory. From there you can copy the file elsewhere and then manipulated it, making sure you clean up by getting rid of the original one saved on the Inbox folder. Class reference available here
Document interaction programming guide available here