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Groups > comp.lang.python > #86092

Re: Design thought for callbacks

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Frank Millman wrote:
> "In order to inform users that certain bits of state have changed, I require 
> them to register a callback with my code."
> 
> This sounds to me like a pub/sub scenario. When a 'listener' object comes 
> into existence it is passed a reference to a 'controller' object that holds 
> state. It wants to be informed when the state changes, so it registers a 
> callback function with the controller.

Perhaps instead of registering a callback function, you
should be registering the listener object together with
a method name.

You can then keep a weak reference to the listener object,
since if it is no longer referenced elsewhere, it presumably
no longer needs to be notified of anything.

-- 
Greg

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Re: Design thought for callbacks "Frank Millman" <frank@chagford.com> - 2015-02-21 07:41 +0200
  Re: Design thought for callbacks Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-02-22 03:15 +1100
    Re: Design thought for callbacks Marko Rauhamaa <marko@pacujo.net> - 2015-02-21 19:08 +0200
      Re: Design thought for callbacks Cem Karan <cfkaran2@gmail.com> - 2015-02-22 07:16 -0500
        Re: Design thought for callbacks Marko Rauhamaa <marko@pacujo.net> - 2015-02-22 14:46 +0200
          Re: Design thought for callbacks Cem Karan <cfkaran2@gmail.com> - 2015-02-22 09:17 -0500
      Re: Design thought for callbacks Laura Creighton <lac@openend.se> - 2015-02-22 13:52 +0100
      Re: Design thought for callbacks Cem Karan <cfkaran2@gmail.com> - 2015-02-22 09:10 -0500
    Re: Design thought for callbacks "Frank Millman" <frank@chagford.com> - 2015-02-22 08:44 +0200
      Re: Design thought for callbacks Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-02-22 23:15 +1300
        Re: Design thought for callbacks Cem Karan <cfkaran2@gmail.com> - 2015-02-22 09:22 -0500
          Re: Design thought for callbacks Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-02-24 18:45 +1300
            Re: Design thought for callbacks Cem Karan <cfkaran2@gmail.com> - 2015-02-24 06:06 -0500
        Re: Design thought for callbacks Ian Kelly <ian.g.kelly@gmail.com> - 2015-02-22 23:57 -0700

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