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Re: How to write hook addon properly.

by Richard deMeester <> - 11/03/2019 23:48:36
Ooh, thankyou Holger,

Being all self taught by trial and error, I thought my solution was elegant enough, but I really do appreciate the more refined solution you have presented.

I do realise that the classes are not instantiated - that was more of a typo caused by lacking the correct way of explaining things.

Also "actually, the framework won't control anything for non-installed modules" - kind-of what I meant - that it will call and control what it needs to, and will ignore and not call what is not installed.

Am I oversimplifying by suggesting that the true difference between between our 2 suggestions is that:
  • my solution will always cause a reassignment of the base method to the new method;
  • the _register_hook solution will cause the reassignment only if the module is installed.
Is there any other difference or benefit?

 # do the patching, and detect if it happend before
I guess this is just a proper fail-safe, because it if is a simple assignment, then it shouldn't matter if it has happened before.  Or does it?


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From: Holger Brunn <>
Sent: Friday, 8 March 2019 5:31 PM
To: Contributors
Subject: Re: How to write hook addon properly.
some nitpickings

> All of the python code is "loaded and available" and the classes are

> instantiated

Odoo loads (as in `import ...`) all code that's in the addon path. It does not 
instantiate the classes defined in non installed modules as in `my_class()`

> whether the module is installed or not - Odoo will control,

> by knowledge of the modules installed, which methods are to be called and

> in which order.

actually, the framework won't control anything for non-installed modules. And 
it can't and it shouldn't. If a module needs monkey patching I'd suggest to do 
this in _register_hook of some model, then you know your module is actually 

For models, Odoo will create python classes on the fly mimicking the 
inheritance chain of the modules installed, so if you have modules A and B 
both having a model inheriting from res.partner, and A depends on B, Odoo will 
carve classes that in python inheritance look somewhat like

B#res.partner (inherits from base#res.partner)
A#res.partner (inherits from B#res.partner)

If you need to do fancy stuff with inheritance, inspect self.__mro__ - this is 
more or less where python stores the chain of functions to call when you say 
super(...). You can also manipulate this programmatically, or call just the 
version of the function you need.

So what the example code should be doing is

class MrpProductProduce(models.TransientModel):
    _inherit = "mrp.product.produce"

    def _register_hook(self):
        # do the patching, and detect if it happend before
        # (models are registered with every registry reload, that can happen
        # on run time too)
        # cf
        return super()._register_hook() # 

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