Re: [Boost-users] [noob] I have pointer, ptr_list::release wants iterator

From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2008-02-26 05:29:09

Szczepan Hołyszewski skrev:
> I have a pointer to an object that is in a ptr_list, and I want to "detach" 
> the object from the list without deleting it.
> 
> Problem: ptr_list::release() wants an iterator, not a pointer.
> 
> A naive attempt at std::finding the iterator fails because ptr_list's 
> indirection kicks in and std::find ends up wanting to compare values instead 
> of pointers. Luckily my objects aren't equality comparable so I get a compile 
> error instead of an elusive bug. As a workaround I just walk the list with 
> BOOST_FOREACH() but it feels kludgy.
> 
> Is there a "designed" way to feed a ptr_list an element pointer and milk the 
> corresponding iterator?

No, you have to search for it.

> Is there a direct way do detach an item from ptr_list without deleting it?
> 
> Did I overlook something obvious?

You can compare pointers by using

   std::find( cont.begin().base(), cont.end().base(), ptr );

.base() returns the wrapped containers iterator.

-Thorsten