Re: [Boost-users] multi_index_container: replace() modifies my iterator

Subject: Re: [Boost-users] multi_index_container: replace() modifies my iterator
From: joaquin_at_[hidden]
Date: 2011-01-10 04:21:26

Nicolas Rannou escribió:
> Thanks, that is what I was suspecting.
>
> Is there already something in boost to do what I intend to do?
> If not, which strategy would you recommend to by pass this issue?
> I got some ideas but nothing straight forward and I would like it to
> be as efficient as possible.
>
> Thanks again,
>
> Nicolas
>

In this particular case, you can do the following:

    Iterator it2 = m_Container.get< CollectionID >().lower_bound( 30 );

    while( it2!=m_Container.get< CollectionID >().end() &&
it2->CollectionID==30)
      {
      int time = it2->TCoord;
      if( time < 500 ) // we want to change the collection ID in this case
        {
        Structure tempStructure(*it2);
        tempStructure.CollectionID = 40;
        m_Container.get< CollectionID >().replace(it2++, tempStructure);
        }
      else ++it2;
      }

I haven't compiled it, but I think it should work. Two notes about the code:

1. Note that in the invocation to replace() we do a post-increment of
it2, so that
it2 points to the following element before the current one is replaced and,
consequently, moved to a new position.
2. The while condition of the loop has changed: as a result of replacements,
it could be the case that modified elements get between the range of
elements with
CollectionID==30 and it3, so checking for it2!=it3 is not safe.

HTH,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo

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