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#575 ✓wontfix
Christopher J. Bottaro

callbacks don't work from extended modules

Reported by Christopher J. Bottaro | July 8th, 2008 @ 06:32 PM | in 2.x

If an AR instance extends a module that adds callbacks to the instance's metaclass, then those callbacks do not get called when the callback chain is invoked.

I have included a patch that fixes the problem as well as adds a test case. All tests pass in activesupport after the patch.

Please see the test case included in the patch for a very clear description of the problem.

This patch is meant to be applied from SRC_ROOT/activesupport with -p0.

This patch is for Rails 2.1.0.

Comments and changes to this ticket

  • Christopher J. Bottaro

    Christopher J. Bottaro July 8th, 2008 @ 06:29 PM

    I forgot to mention, this patch is for Rails 2.1.0.

  • Pratik

    Pratik July 14th, 2008 @ 02:49 PM

    • Assigned user set to “josh”
  • Repository

    Repository July 16th, 2008 @ 03:58 AM

    • State changed from “new” to “resolved”

    (from [be078ee162fcae883a5621a30929879cd783a238]) Run callbacks from object's metaclass [#575 state:resolved]

  • josh

    josh July 17th, 2008 @ 03:26 AM

    • State changed from “resolved” to “open”

    We had to revert this. Apparently it broke a ton of shit.

    Maybe we don't want callbacks on the metaclass, but a set of callbacks for objects as well as classes.

    Lets try a new API

    module ModuleWithCallbacks
      def self.extended(obj)
        obj.before_save :module_callback
      def module_callback
        # ...
    p =
    # or also do
    p.before_save :module_callback
    def p.module_callback

    We could have a instance variable on the object that tracks its callbacks

  • Christopher J. Bottaro

    Christopher J. Bottaro July 17th, 2008 @ 03:55 AM

    Just out of curiosity, what did it break?

    It broke our webapp because we try to serialize AR instances and it complained about not being able to serialize the object's metaclass. We just decided that we shouldn't have been serializing AR instances in the first place, heh.

  • Christopher J. Bottaro

    Christopher J. Bottaro July 17th, 2008 @ 03:59 AM

    Btw, your solution of having callback chains on classes as well as instances of classes (objects) sounds great.

  • josh

    josh July 19th, 2008 @ 01:30 AM

    Check out the latest Memoizable stuff for reference.

    I've been playing around with a pattern that works for Classes and Objects.

    I don't have time to work on this right now, but I do plan to get back to in in the next coming weeks.

    (BTW, I'm getting obsessed with "object-oriented"/prototype driven development)

  • josh

    josh July 22nd, 2008 @ 04:30 PM

    • State changed from “open” to “wontfix”

    It looks like this is going take alot more work. If you ever decide its worth pursuing, open and new ticket for refactoring Callbacks and assign it to me.

  • klkk

    klkk May 23rd, 2011 @ 03:00 AM

    • Importance changed from “” to “”

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