For short, declare UTImportedTypeDeclarations(for types that are not predefined as System Uniform Type Identifiers), CFBundleDocumentTypes in Info.plist, UIApplicationLaunchOptionsURLKey in
[launchOptions valueForKey:UIApplicationLaunchOptionsURLKey]
And for multitask apps, additionally respond to
(BOOL)application:(UIApplication *)application openURL:(NSURL *)url sourceApplication:(NSString *)sourceApplication annotation:(id)annotation // for iOS 4.2+
or
(BOOL)application:(UIApplication *)application handleOpenURL:(NSURL *)url // for iOS 2.0+, deprecated.
One little trick to handle ALL file types:
<key>CFBundleDocumentTypes</key> <array> <dict> <key>CFBundleTypeName</key> <string>All Files</string> <key>LSItemContentTypes</key> <array> <string>public.data</string> <string>public.content</string> </array> </dict> </array>
