Custom UTI Not opening in App - objective-c

Question

I am trying to create a new document UTI for my App so that people can share points of interest with others. From what I can understand on SO, Tutorials, and from Apple's documentation, you need to do the following:
Create a Document Type in the .plist
Create an Exported UTI that corresponds with it
Use the method: -(BOOL)application:(UIApplication *)application
didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
From what I understand, as long as you did those right, you should be able to open the file through Mail without any problems. Unfortunately it isn't working for my own custom UTIs. I DO see my App in the list of "Open with..." in Mail, but when I select it, my App doesn't open at all. It just dosen't do anything at all not only when the App isn't open, but when the App is open. Mail stays up and nothing happens at all. I also checked the console using "Organizer" and there is absolutely nothing that happens.
Originally I thought my plist was wrong, so I tested opening a public UTI (I added the com.adobe.pdf document type) and my app launched just fine (though it promptly crashed because I don't actually support PDFs ;)). But the point was that it launched without any problem.
The only thing I can think of that might be a problem is HOW I am creating the file. I am creating the file in an email by the use of this method (also in the App to export):
MFMailComposeViewController *picker = [[[MFMailComposeViewController alloc] init] autorelease];
[picker setSubject:[NSString stringWithFormat:#"My place: %#",POIName]];
[picker addAttachmentData:customPOIData mimeType:#"application/customPOI" fileName:[NSString stringWithFormat:#"%#.icp",POIName]];
[picker setMessageBody:#"Check out this great place I found!" isHTML:NO];
[picker setMailComposeDelegate:self];
[self presentModalViewController:picker animated:YES];
Is there anything wrong with that?
Also, here is my plist code:
CFBundleDocumentTypes:
<key>CFBundleDocumentTypes</key>
<array>
<dict>
<key>CFBundleTypeIconFiles</key>
<array/>
<key>CFBundleTypeName</key>
<string>Custom POI</string>
<key>CFBundleTypeRole</key>
<string>Viewer</string>
<key>LSHandlerRank</key>
<string>Owner</string>
<key>LSItemContentTypes</key>
<array>
<string>com.imadev.icp</string>
</array>
</dict>
</array>
UTExportedTypeDeclarations:
<key>UTExportedTypeDeclarations</key>
<array>
<dict>
<key>UTTypeConformsTo</key>
<array>
<string>public.data</string>
</array>
<key>UTTypeDescription</key>
<string>Custom POI</string>
<key>UTTypeIdentifier</key>
<string>com.imadev.icp</string>
<key>UTTypeTagSpecification</key>
<dict>
<key>public.filename-extension</key>
<array>
<string>icp</string>
</array>
<key>public.mime-type</key>
<string>application/customPOI</string>
</dict>
</dict>
</array>
Thanks a lot for any help!!
-Mark

Answer 1

I finally figured out what was wrong by pulling apart all the code.
When I change "public.filename-extension" to a string and not an array of strings it works. Don't ask me why... I think it's strange we can't use an array of file extensions. But apparently that was it.
Any ideas as to why that happened?

Answer 2

In my case, I could keep filename-extension as an array without problems. Instead, it was the 'public.data' that was the issue. I switched to 'public.image' and then had jpg, jpeg, and png as file extensions, and it suddenly worked.