Re: [Boost-users] [fusion][?] a dictionary with compile time (or types as) keys

Subject: Re: [Boost-users] [fusion][?] a dictionary with compile time (or types as) keys
From: Larry Evans (cppljevans_at_[hidden])
Date: 2014-02-17 08:20:47

On 02/16/14 12:30, Nick Stokes wrote:
> The problem is the following:
>
> class TypeDictionary {
> public:
>     // implementation be here -- and the question is about this
> };
>
> struct Foo;
> struct Bar;
>
> void userOfTypeDictionary() {
>
>      TypeDictionary td;
>      td.insert( Foo() );
>      td.insert( Bar() );
>      td,insert( double(3.14) );
>      // and other unknown (to TypeDictionary)
>      // list of types attached
>
>      // later on, in a different scope perhaps
>      Foo& f = td.get<Foo>() ;
>      Bar& f = td.get<Bar>();
>      double pi = tg.get<double>();
>      // ...
> }
>
>
> Now the question so far seems like right up in the alley of
> Boost.Fusion, perhaps with a boost::fusion::set, but I am unsure how to
> manipulate a set of types unknown ahead of time as in code above, and
> with a  -- rather obvious -- extension whereby different instances of
> TypeDictionary   would be used to contain a different set of types,
> potentially in different compilation units.
>
>
> As for a realistic motivating use case, think of a  plugin manager. At
> any given time of its life an arbitrary heterogeneous set of  objects
> are attached to it, and the it is the manager's job to manage the life
> time of the attached objects and return (a reference) to them when
> queried in a type-safe manner.
>
>
> Any ideas on whether such a thing is possible, and how, would be deeply
> appreciated.
>
> Thanks many,
> Nick
>
Wouldn't:

http://www.boost.org/doc/libs/1_55_0/libs/fusion/doc/html/fusion/container/map.html

work?

-regards,
Larry