4 years later, I found this and wanted to note it helped me. (Having a file open with "import SwiftUI.")
That said, it's the most unintuitive/asinine thing I've seen in a while. If I have a pinned preview, I can still see the canvas no matter what file is open. Then if I close the canvas, I can't open it again! But if I go to a file with "import SwiftUI," I can. And the pin is still there.
Apple should fix it so it's not gated at all. Or when I turn the Canvas on in an "invalid" file, say so
geoffhom
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution
Last seen
User for
From
Van, TX