Re: [Boost-users] [multi_index] doing insert() within iteration over equal_range() result?

27 Oct 2008


      
...
Date: Thu, 23 Oct 2008 16:50:15 +0200
From: joaquin@tid.es
To: boost-users@lists.boost.org
Subject: Re: [Boost-users] [multi_index] doing insert() within iteration over equal_range() result?
Prometheus Prometheus escribió:
...
Hi all,
i have the following problem:
i use multi_index like this
        std::pair range;
range = this->events.get().equal_range(boost::make_tuple(event,condition));
while(range.first!=range.second){
    // CALL an event handler!
    this->callEventHandler(range.first);   // << this shows just how it works, its not exactly my code
    ++range.first;
}
within the callEventHandler and its called functions its possible that the event handler wants to register new events which results to this:
this->events.insert(eventdata);
The problem is OR can be, that the insert modifies the indices which modify the range.first iterators and thus a ++range.first results in an invalid "next" element
this makes sense and i think most of you know this and had this problem already
Questions:
Does anyone have a good idea/solution how to solve this situation correctly so that the range i received will be valid?
I think the easiest solution is to save copies of the iterators in range 
before you
start the loop:
range = this->events.get().equal_range(boost::make_tuple(event,condition));
std::vector buff;
  while(range.first!=range.second)buff.push_back(range.first++);
for(std::size_t n=0,s=buff.size();n     // CALL an event handler!
    this->callEventHandler(buff[n]);
  }
HTH,
Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo
hmm, great and easy solution, thx!
but just to get better knowledge of (boost) iterators
1. what distinguishes 2 iterators of the same type?
to ask it differently: given are 2 multi_index objects storing the same information
2. find() using the same search values will give me results on both objects - can i store the iterators in a vector OR a std::set without a problem? or will there be conflicts between the iterators, cause they are pointing to the same datatype?
3. is obj1.end()==obj2.end() true?

thx @ ll
_________________________________________________________________
Discover the new Windows Vista
http://search.msn.com/results.aspx?q=windows+vista&mkt=en-US&form=QBRE