Re: [Pyobjc-dev] more on beginSheet

[Ronald O. <ous...@ci...>]

On Friday, Jan 31, 2003, at 01:09 Europe/Amsterdam, David Eppstein 
wrote:

> I worked around the missing selector by passing "missingSelector:" as 
> the argument.
> Since it shouldn't get called without a modalDelegate, that should be 
> ok as a workaround.
> Next question: why is the selector for the contextInfo: argument 'i'?  
> The objc spec is for this to be a (void *), but I am prevented from 
> passing None here (workaround: pass 0 instead).

We use an int argument instead of a (void*) argument on purpose. The 
only reasonably valid alternative would be to require a buffer-like 
object (or None for a NULL  pointer). Even then you would be required 
to store a reference to that buffer-like object somewhere, otherwise 
the buffer might be garbage collected before your callback is called.

When we first ran into this problem we did choose the current solution 
because this (a) makes it explicit that you must keep a reference to 
the data you want to use and (b) you cannot cause memory corruption by 
not following the rules (which might happen if we did expose 
contentInfo as a pointer).

Ronald