Re: [Boost-users] Collecting boost multi-index meta data

Thanks a lot. I think this should do. Thanks, Gokul. On Thu, Mar 24, 2011 at 7:13 PM, wrote:

Gokulakannan Somasundaram escribió:

Hi Joaquín ,

...

I am extremely sorry, i missed your mail. First of all thanks a lot for replying.

No problem. Please don't top-post: http://www.boost.org/community/policy.html#quoting

I have fixed the issue for now. But i am actually explaining the issue

...

i had. Please take a shot at it. Say i have an object and i have created multi index on some members of the object. Now since, this is being used in a multi-threaded code, i will acquire a mutex on the whole multi-index, only if i have updated those attributes involved in the multi-index build. Else i won't take the mutex. Now my problem is, i have multi-indexed many such classes. what is the best way to check whether the updated attribute is part of multi-index. Currently we have written a python code which scans the C++ files and creates a list of attribute numbers ( each member attribute has a number associated with it ). Whenever there is an update, we check against the list produced by the python code in C++. My question was if there is a way to do this within C++ itself.

If we had the following metafunction to check whether a particular key extractor is used with a multi_index_container or not:

template struct is_key_extractor_of{};

then it is easy to know at compile time if a particular member of a class is referenced by a member<...> key extractor (composite keys are harder and left as an exercise to the reader):

struct A { int a,b,c,d,e,f; };

typedef multi_index_container< int, indexed_by< ordered_unique >, sequenced<>,

...

multi_t;

BOOST_MPL_ASSERT ((is_key_extractor_of,multi_t>)); BOOST_MPL_ASSERT_NOT((is_key_extractor_of,multi_t>));

Full code provided in the attachment. Does this help to implement your scenario?

Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

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