> Whose_ destructor, if not the receiving-type
The receiving type should control the lifetime of any callbacks to itself that it gives away. The destructor is the best place to ensure this gets properly cleaned up.
Like anything, custom callbacks can be used well or misused. Design is a matter of expertise and taste bordering on an art form. Connecting framework implementation and business logic can be done cleanly or clumsily. I am skeptical of an argument that callbacks have a code smell prima facie.
I don't disagree, but the article does. RH describes an architecture where setup functions create callbacks, independent of the receiving type. If I were to steelman him, it would be something like this: "in a pedantic MVC system, model objects don't depend on view objects by design, and therefore should not be aware that their methods are used as 'click callbacks'"