[Pyrex] classes and callbacks

[Lenard Lindstrom]

On 11 Oct 2006 at 15:45, Test Drive wrote:

> 
> Hi All,
> 
> Thanks for considering this. I think Lenard Lindstrom got it pretty 
> right.
> Greg, consider callabcks which take functions as parameters.
> 
> gobj_callback_resize(gobj *g, void (*func) (gobj *g);
> 
> Here if there are 10 instances of the class , each registering a diff 
> function for the cb, I need to keep track of which instance 
> registered which function.
> I use a global dict with instance_id as key and the callback func as 
> value. 
> 
> The workaround by Lenard Lindstrom is pretty good. Look at the cb 
> example, I need to have gobj *g in both the classes and way (sandwich 
> function) to copy the pointer from one class to other.
> 
> Sure if the callback is implemented it will make the code much 
> cleaner. 
> psuedo code will look something like this
> 
> cdef extern from "g.h"
>  gobj_callback_resize(gobj *g, void (*func) (gobj *g))
> 
> cdef class ABC:
>  cdef gobj *g
> 
>  def __init__(self):
>  self.g=init_gobj()
>  self.resize_callback=None
>  
>  cdef callback cb_func (gobj *g):
>  
> do_anything_here_u_have_access_to_ptr_g_based_on_which_u_can_call_othe
> r_c_funcs_of_the_lib_or_manipulate_this_instance's_attributes 
> 
>    def register_resize_callback(python_callback_func):
>        self.resize_callback=python_callback_func  
>  
>  gobj_callback_resize(self.g,self.cb_func)
> 
> Thanks
> 
I think you want to use a bound method as a C callback function. You 
can do this with the ctypes module.

Lenard Lindstrom
<len-l at telus.net>