Re: [Boost-users] multi_index_container for composite key

Subject: Re: [Boost-users] multi_index_container for composite key
From: joaquin_at_[hidden]
Date: 2010-09-09 05:21:23

Uthpal Urubail escribió:
> Joaquín,
> My question is:
> Can I define container like below?
> typedef multi_index_container<
>     ElemShell*,
>     indexed_by<
>     //non-unique as some  might have more than ids
>     ordered_non_unique<
>         composite_key<
>             ElemShell*,
>             member<ElemShell,int,&ElemShell::N1>,
>             member<ElemShell,int,&ElemShell::N2>,
>             member<ElemShell,int,&ElemShell::N3>,
>             member<ElemShell,int,&ElemShell::N4>
>             >
>     >,
>     ordered_unique<
>     member<GeneralElement,int,&GeneralElement::EID>
>     >
>     >
>   
>> beambook;
>>     

Yes, you can (except that the second index seems to be wrongly keyed
on GeneralElement rather than ElemShell, but I understand this is a typo.)

> When I retrieve,
>         beambook::iterator it=(pb.find(boost::make_tuple(obj->N1,obj->N2,obj->N3,node4)));
>         int val = (*it)->N4;
> 	Application is crashing.
>   

Almost surely because there's no element with the provided N1,N2,N3,N4
and hence the iteraror it is pb.end().

> About: If you use ordered_unique then there cannot be two elements with the same node[0], node[1], node[2] values. 
> Its TRUE. Two elements cannot have same node[0], node[1], node[2] values. How should be the container?
>   

Use ordered_unique then, as your own statements imply.

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo