In a larger ObjC/Swift-mixed codebase I have an ObjC protocol MyObjCProtocol <NSObject> that other ObjC classes need to conform to. It declares a string property @property (copy) NSString *myString.

Now, one of my Swift objects has a property conformsToObjCProtocol that is declared conforming to this protocol:

let conformsToObjCProtocol: MyObjCProtocol

This all works well.
But when I try to observe myString using Combine like this:

let cancellable = conformsToObjCProtocol.publisher(for: .myString).sink { print($0) }

I get an error Value of type 'any MyObjCProtocol' has no member 'publisher'.

I believe it should work because MyObjCProtocol is declared conforming to NSObject. I did add MyObjCProtocol.h to the bridging header too so that’s not it. I can’t rewrite the protocol in Swift because I need ObjC classes to conform to it. What can I do about this?