Re: [Boost-users] [multi-index] Key extractor for 1:n relationship?

Subject: Re: [Boost-users] [multi-index] Key extractor for 1:n relationship?
From: plarroy (plarroy_at_[hidden])
Date: 2009-07-17 01:12:00

Boris Schaeling wrote:
> All the key extractors in the documentation of Boost.MultiIndex return 
> one value for an element in a container. Is it somehow possible to use 
> a 1:n relationship between element and value?
>
> The documentation uses this container definition (among others):
>
> typedef multi_index_container<
>   employee,
>   indexed_by<
>     hashed_unique<
>       const_mem_fun<employee, std::string, &employee::name>
>     >
>   >
>> employee_set;
>
> Let's assume an employee can have more than one name (std::string 
> becomes std::vector<std::string>). Now if someone searches for Tom or 
> John the same employee should be returned by the container. Is this 
> possible?
>

A vector of strings is still an object, and hashed_unique indexes are 
unique. For indexes that allow duplicate items you want "equal_range" like:

typedef pmt_t::index<pid>::type pid_idx_t;
pair<pid_idx_t::iterator,pid_idx_t::iterator> pid_match = 
pid_idx.equal_range(50);
while(pid_match.first != pid_match.second ) {
}

Regards.

Pedro.

> Boris
>
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