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

Subject: Re: [Boost-users] [multi_index] doing insert() within iteration over equal_range() result?
From: joaquin_at_[hidden]
Date: 2008-10-23 10:50:15

Prometheus Prometheus escribió:
> Hi all,
>
> i have the following problem:
> i use multi_index like this
>         std::pair<Plugins::pEvents::index::type::iterator,Plugins::pEvents::index::type::iterator> 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<Plugins::pEvents::index::type::iterator> buff;
  while(range.first!=range.second)buff.push_back(range.first++);

  for(std::size_t n=0,s=buff.size();n<s;++n){
    // CALL an event handler!
    this->callEventHandler(buff[n]);
  }

HTH,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo