Question

Ive got a large bunch of objects (potentially 1000’s) which I need to store in a container. I need to be able to find specific instances in two ways, either by its ID number (64bit unsigned int), or its name (std::string). Generally by ID will be the most common, however in some cases the name is known, but not the ID.

std::map can provide a single <-> value, however I’m not sure if having 2 sets of std::map containers, one for the Ids and another for the strings is the best approach here.

EDIT – REVISED code and error:

Ok, I figured i’d give the multi index a try since I have boost anyways, however I can’t seem to get it to compile even though I’ve done it exactly the same as in the documentation as far as I can tell 🙁

test code:

namespace common
{
    class MyBaseClass
    {
    public:
        typedef boost::uint64_t Id;

        //name and id are constant, at least for the period im intrested in
        //when I want it in the container...
        const std::string &getName()const{return name;}
        Id getId()const{return id;}

        ...other stuff...
    };
}

class MyClass : public common::MyBaseClass
{
    ...other stuff...
};

typedef boost::multi_index_container
<
    MyClass*,
    boost::indexed_by
    <
        boost::ordered_unique<boost::const_mem_fun<MyBaseClass, MyBaseClass::Id,    &MyBaseClass::getId  > >,
        boost::ordered_unique<boost::const_mem_fun<MyBaseClass, const std::string&, &MyBaseClass::getName> >
    >
>MyClassList;

and your average boost template error…

c:\lib\c++\boost\boost\aligned_storage.hpp(69) : error C2872: ‘detail’ : ambiguous symbol
could be ‘boost::detail’
or ‘boost::multi_index::detail’
c:\lib\c++\boost\boost\multi_index\detail\index_node_base.hpp(42) : see reference to class template instantiation ‘boost::aligned_storage’ being compiled
with
[
size_=4,
alignment_=4
]
c:\lib\c++\boost\boost\multi_index\detail\index_node_base.hpp(47) : see reference to class template instantiation ‘boost::multi_index::detail::pod_value_holder’ being compiled
with
[
Value=MyClass *
]
c:\lib\c++\boost\boost\multi_index\detail\ord_index_node.hpp(582) : see reference to class template instantiation ‘boost::multi_index::detail::index_node_base’ being compiled
with
[
Value=MyClass *,
Allocator=std::allocator
]
c:\lib\c++\boost\boost\multi_index\ordered_index.hpp(137) : see reference to class template instantiation ‘boost::multi_index::detail::ordered_index_node’ being compiled
with
[
Super=boost::multi_index::detail::index_node_base>
]
c:\lib\c++\boost\boost\multi_index\ordered_index.hpp(119) : see reference to class template instantiation ‘boost::multi_index::detail::ordered_index’ being compiled
with
[
KeyFromValue=boost::multi_index::const_mem_fun,
Compare=std::less,std::allocator>>,
SuperMeta=boost::multi_index::detail::nth_layer<2,MyClass *,boost::multi_index::indexed_by>,boost::multi_index::ordered_unique>>,std::allocator>,
TagList=boost::mpl::vector0,
Category=boost::multi_index::detail::ordered_unique_tag
]
c:\lib\c++\boost\boost\multi_index_container.hpp(86) : see reference to class template instantiation ‘boost::multi_index::detail::ordered_index’ being compiled
with
[
KeyFromValue=boost::multi_index::const_mem_fun,
Compare=std::less,
SuperMeta=boost::multi_index::detail::nth_layer<1,MyClass *,boost::multi_index::indexed_by>,boost::multi_index::ordered_unique>>,std::allocator>,
TagList=boost::mpl::vector0,
Category=boost::multi_index::detail::ordered_unique_tag
]
c:\projects\bad_angle_studios\brak3\trunk\source\source\server\MyClass.cpp(18) : see reference to class template instantiation ‘boost::multi_index::multi_index_container’ being compiled
with
[
Value=MyClass *,
IndexSpecifierList=boost::multi_index::indexed_by>,boost::multi_index::ordered_unique>>
]
c:\lib\c++\boost\boost\aligned_storage.hpp(53) : error C2872: ‘detail’ : ambiguous symbol
could be ‘boost::detail’
or ‘boost::multi_index::detail’
c:\lib\c++\boost\boost\aligned_storage.hpp(56) : see reference to class template instantiation ‘boost::detail::aligned_storage::aligned_storage_imp::data_t’ being compiled
with
[
size_=4,
alignment_=4
]
c:\lib\c++\boost\boost\aligned_storage.hpp(69) : see reference to class template instantiation ‘boost::detail::aligned_storage::aligned_storage_imp’ being compiled
with
[
size_=4,
alignment_=4
]
c:\lib\c++\boost\boost\aligned_storage.hpp(73) : error C2872: ‘detail’ : ambiguous symbol
could be ‘boost::detail’
or ‘boost::multi_index::detail’
c:\projects\bad_angle_studios\brak3\trunk\source\source\server\MyClass.cpp(44) : error C2676: binary ‘[‘ : ‘MyClassList’ does not define this operator or a conversion to a type acceptable to the predefined operator

Answer 1

boost::multi_index is the answer to your problem. See there for more information on how to use it.