Re: [Boost-users] [multi-index] member arguments [Was: how to use inheritmember as index]

From: Filip Konvička (filip.konvicka_at_[hidden])
Date: 2007-06-28 04:13:00

Joaquín Mª López Muñoz (28.6.2007 9:49):
> Filip Konvi?ka ha escrito:
> [...]
>
>   
>> I use this template in my code:
>>
>>   template<typename T>
>>   struct get_pointer_to_member_details;
>>
>>   template<typename Class, typename Member>
>>   struct get_pointer_to_member_details<Member Class::*> {
>>     typedef Class   class_type;
>>     typedef Member  member_type;
>>   };
>>
>> Using this, you can write (and I do) something like
>>
>>   template<typename MemberPointerType>
>>   struct member {
>>     MemberPointerType pMember;
>>     typedef typename
>> get_pointer_to_member_details<MemberPointerType>::class_type   class_type;
>>     typedef typename
>> get_pointer_to_member_details<MemberPointerType>::member_type  result_type;
>>
>>     member(MemberPointerType pMember) : pMember(pMember) {}
>>    // ...
>> }
>>
>> I wonder then, is it MSVC 8 that allows something non-standard, or is it
>> OK? I think I tried with recent gcc as well and it worked...
>>     
>
> Your code is fine, but it does not do what boost::multi_index::member is
> meant to do, namely accepting the pointer-to-member as a template
> parameter --rather, you're taking it as a runtime variable in construction
> time.
Ah, I see...but duplicating the argument using a macro might work, like 
this:

#define MEMBER(MemPtr) member<get_details<MemPtr>::class_type, 
get_details<MemPtr>::member_type, MemPtr>

The reason why I think this is better is that when you change the member 
type in class declaration, you have to go through all member<> usages 
and change the type there too.

So I guess I can define this macro if I want to use it :-)

Cheers,
Filip