In my application, I wanted to include the QuickLook plugin, which reads a non-system extension, and other applications also use it (let's use RAR for this example). I declare the extension as Exported UTIin my Info package Info.plist as follows:
<key>UTExportedTypeDeclarations</key>
<array>
<dict>
<key>UTTypeConformsTo</key>
<array>
<string>public.data</string>
<string>public.archive</string>
<string>com.rarlab.rar-archive</string>
</array>
<key>UTTypeDescription</key>
<string>Custom RAR Archive</string>
<key>UTTypeIdentifier</key>
<string>com.my-company.rarx-archive</string>
<key>UTTypeTagSpecification</key>
<dict>
<key>public.filename-extension</key>
<array>
<string>rarx</string>
</array>
</dict>
</dict>
</array>
And I also import RAR UTI accordingly:
<key>UTImportedTypeDeclarations</key>
<array>
<dict>
<key>UTTypeConformsTo</key>
<array>
<string>public.data</string>
<string>public.archive</string>
</array>
<key>UTTypeDescription</key>
<string>RAR Archive</string>
<key>UTTypeIconFile</key>
<string>RAR</string>
<key>UTTypeIdentifier</key>
<string>com.rarlab.rar-archive</string>
<key>UTTypeTagSpecification</key>
<dict>
<key>public.filename-extension</key>
<array>
<string>rar</string>
<string>rarx</string>
</array>
</dict>
</dict>
</array>
RARX files seem to never be associated with my application after launch. To check the association I used mdlsas follows:
mdls -name kMDItemContentTypeTree "/Users/Me/.../A File.rarx"
>>> kMDItemContentTypeTree = (
"com.another-company.rarx-archive",
"public.data",
"public.item",
"public.archive"
)
UTI (com.my-company.rarx-archive) ? , , Quick Look , com.another-company.rarx-archive UTI. - , . qlmanage .