Looks like you have to define as a class var
see h ttps://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Properties.html
For computed type properties for class types, you can use the
classkeyword instead to allow subclasses to override the superclass’s implementation. The example below shows the syntax for stored and computed type properties:
Also found an interesting discussion here:
Hope that helps.
Thanks for you help, maybe it's wrong question, the question should be Why Can't Overriding Superclass Property Observers?
I made some investigations according to the information you provided,
Apple says in https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Inheritance.html, chapter Overriding Property Observers:
You can use property overriding to add property observers to an inherited property. This enables you to be notified when the value of an inherited property changes, regardless of how that property was originally implemented.
So, you could file a bug:
- to Apple
- to Swift forum
Thanks for the feedback.
Note: those illegal characters in the forum are really messy