You should better use Code Block properly. More readable code would appeal to more readers.

Can you show your tried code? I cannot reproduce the same layout using Section.

I think the latter is my problem. I believe so. Have you tried using startAccessingSecurityScopedResource as suggested here?

You wrote my iOS app in your opening post, and there are no UIViewController available for Mac. What are you trying to do? You are not interested in using UIViewController  any more?

I mean the code including Section which you tried. Or am I mistaking something and you have not tried Section yet?

I mean the code including Section which you tried. Sorry, if my words were not enough.

@EDD_HID, thanks for the info. I have read some reports that the similar error shown even when BUILD_LIBRARY_FOR_DISTRIBUTION is set. But could not find what would be the right solution for that. Anyway, you need to set BUILD_LIBRARY_FOR_DISTRIBUTION to YES to distribute a binary library, so please try and find info under that setting.

I want to save the state when there is a change to the switch state You should better have clarified it in the opening post.

Fragments of code does not help you finding what to change. container is not initialized, how and where are you setting it? Just before the save() is called? Or somewhere which may be called earlier? Please show the complete code.

Is the information I provided here enough to be able to show that Far from enough. Please show your complete code, adding some images explaining how you have set up Core Data entities. Or you expect all the readers to read the same book?

Please confirm, all the lines you have show here are placed in the same method? In which method you wrote these lines is very important to find what to change.

It may be because your MyViewB is broken. Please show the complete code to reproduce the issue.

Can you share the complete code which includes startAccessingSecurityScopedResource you tried?

You are using Float which is declared as Int16, so data.setValue(Float(collectionSize), forKey: "defaultSize") does not make sense. Do you really understand you cannot change the type of the attribute dynamically? And once I leave that view and come back, my update never got saved. It goes back to the original defaultValue., nothing sure can be said without seeing all the view transition codes.

Have noticed I have added @escaping on the first line?