Registering the File Types Your App Supports

If your app is capable of opening specific types of files, you should register that support with the system. This allows other apps, through the iOS document interaction technology, to offer the user the option to hand off those files to your app.

To declare its support for file types, your app must include the CFBundleDocumentTypes key in its Info.plist property list file. (See Core Foundation Keys.) The system adds this information to a registry that other apps can access through a document interaction controller.

The CFBundleDocumentTypes key contains an array of dictionaries, each of which identifies information about a specific document type. A document type usually has a one-to-one correspondence with a particular file type. However, if your app treats more than one file type the same way, you can group those file types together to be treated by your app as a single document type. For example, if you have an old and new file format for your application’s native document type, you could group both together in a single document type entry. This way, old and new files would appear to be the same document type and would be treated the same way.

Each dictionary in the CFBundleDocumentTypes array can include the following keys:

• CFBundleTypeName specifies the name of the document type.

• CFBundleTypeIconFiles is an array of filenames for the image resources to use as the document’s icon.

• LSItemContentTypes contains an array of strings with the UTI types that represent the supported file types in this group.

• LSHandlerRank describes whether this application owns the document type or is merely able to open it. (For a list of values for LSHandlerRank, see CFBundleDocumentTypes.)

From your app’s perspective, a document is a file type (or file types) that the application supports and treats as a single entity. For example, an image processing application might treat different image file formats as different document types so that it can fine tune the behavior associated with each one. Conversely, a word processing application might not care about the underlying image formats and just manage all image formats using a single document type.

Listing 1 shows a sample XML snippet from the Info.plist of an app capable of opening a custom file type. The LSItemContentTypes key identifies the UTI associated with the file format and the CFBundleTypeIconFiles key points to the icon resources to use when displaying it.

Listing 1  Document type information for a custom file format

<dict>

   <key>CFBundleTypeName</key>

   <string>My File Format</string>

   <key>CFBundleTypeIconFiles</key>

       <array>

           <string>MySmallIcon.png</string>

           <string>MyLargeIcon.png</string>

       </array>

   <key>LSItemContentTypes</key>

       <array>

           <string>com.example.myformat</string>

       </array>

   <key>LSHandlerRank</key>

   <string>Owner</string>

</dict>

For more information about the contents of the CFBundleDocumentTypes key, see the description of that key in Information Property List Key Reference.