Registering an icon for my application's document type

Question

I'm trying to register an icon for my app's document type. After reading Declaring New Uniform Type Identifiers and looking at /Developer/Examples/Sketch I came up with something like this in my Info.plist:

<key>CFBundleDocumentTypes</key>
<array>
  <dict>
    <key>CFBundleTypeRole</key>
    <string>Viewer</string>
    <key>LSItemContentTypes</key>
    <array>
      <string>com.mycompany.myextension</string>
    </array>
    <key>NSDocumentClass</key>
    <string>NSString</string>
  </dict>
</array>

...

<key>UTExportedTypeDeclarations</key>
<array>
  <dict>
    <key>UTTypeDescription</key>
    <string>Blah blah blah</string>
    <key>UTTypeConformsTo</key>
    <array>
      <string>public.data</string>
    </array>
    <key>UTTypeIconFile</key>
    <string>My-file-icon.icns</string>
    <key>UTTypeIdentifier</key>
    <string>com.mycompany.myextension</string>
    <key>UTTypeTagSpecification</key>
    <dict>
      <key>public.filename-extension</key>
      <array>
        <string>myextension</string>
      </array>
    </dict>
  </dict>
</array>

Now, everything is fine and dandy, i.e. my program is opened when I click on a file with my extension, etc. However, the document icon is not registered with the OS, i.e. I see an ugly blank icon instead of my beautiful My-file-icon.icns. I suspect that I'm missing something in the plist above, any ideas?

Answer 1

Try putting the icon name in the CFBundleTypeIconFile key in the CFBundleDocumentTypes array, not in the UTExportedTypeDeclarations array.

And of course make sure that "My-file-icon.icns" is in your target's Copy Bundle Resources build phase and is being copied into Contents/Resources in your app's bundle.

Answer 2

Your UTI declaration in the Info.plist appears to be correct, however I noticed an other issue. If you application is a document-based application you need to replace the NSString in following entry with your NSDocument subclass:

<key>NSDocumentClass</key>
<string>NSString</string>

For example it's "SKTDocument" in Sketch:

<key>NSDocumentClass</key>
<string>SKTDocument</string>

Edit: Please also make sure to use your own reverse domain name for your exported UTIs. This ensures that UTIs are unique. For example its com.mindnode.MindNode.MindNodeDocument in my case.

Answer 3

I've been trying to do this in Xcode 11 and it's been a challenge. There are lots of answers here on SO to questions like this but I couldn't find one that had everything I needed to get this working. I'll try to do that here.

Technical Q&A QA1587 Although this is a bit old I think it has everything required but it's a bit vague in some spots like when it says Provide an icon for the document.

I thought I could make it work with an icon in Assets.xcassets but it didn't work for me until I provided an icns file. I took the 1024x1024 png app icon and converted it to an icns here at cloudconvert. Then I added that icns to my project. I don't think it matters where you put it. I put it just below the top level. It's circled in the image below.

Follow the arrows in the image and you end up at the Info tab. I tapped the Add button to create a Document Type and filled it in as shown. When you tap the Add button in the icon section it will ask you for an icns file. Once I had mine in the project it appeared in the window and I could select it.

Same for Configured UTIs.

That was it. In Files, Messages, or Mail the icon appears.