I've written an audio unit which I've been testing by loading it in the application from the sample code (https://developer.apple.com/library/content/samplecode/AudioUnitV3Example/Introduction/Intro.html).
The good part
All audio processing works as expected.
The problem
The audio unit extention's view doesn't show. The extension is registered as having a UI, by the NSExtensionPointIdentifier property being set to
com.apple.AudioUnit-UI, and the sample code host will open the custom view pane, but the UI is simply blank.
The frustration
As said, the audio is being processed, but the UI doesn't appear. And to make matters worse; there is no errors reported, so it's difficult to troubleshoot.
The question
Why? — What is wrong, since the audio unit won't show its UI?
There seems to be some discrepancies in the documentation as to why this could be happening.
One place states that it's all about the plist, opting in or out for UI:
"The name of the main storyboard file for the Audio Unit app extension. This key is required unless you are specifically creating an Audio Unit app extension without a user interface. In that unusual case, use the
NSExtensionPrincipalClassHowever, the sample code, does not follow this documentation, as it uses NSExtensionPrincipalClass in its plist.
I've tried both ways though, none of them work. I've even tried to strip the filter demo code down to what I have in mine, gradually taking away pieces to see when it fails to produce the UI — no luck finding the "magic" that makes the UI appear.
I expect I'm missing something. Hard to tell what though, when there is no error reported.
