Re: [Boost-users] [multi_index] modify~~

Subject: Re: [Boost-users] [multi_index] modify~~
From: isjk (isjk_at_[hidden])
Date: 2010-08-03 02:40:19

it compiled error!
I redefined "channel_table_pr_view" like this,
 typedef multi_index_container<
    channel*,
    ordered_non_unique<
       key_from_key<
           BOOST_MULTI_INDEX_MEMBER(peer, int guid_),
           BOOST_MULTI_INDEX_MEMBER(channel, peer* pr_)
       >
  > channel_table_pr_view;
and insert some element like this,

peer_table pt_;
const peer* pr1_ = *&(pt_.insert(peer(1)).first);
const peer* pr2_ = *&(pt_.insert(peer(2)).first);
  ... other 1000000
channel_table ct_;
ct.insert(channel(1, pr1_, 0));
ct.insert(channel(2, pr2_, 2));
ct.insert(channel(3, pr3_, 4));
  ... other 100000

nth_index<channel_table, 0>::type ic0,ic1; 
boost::tie(ic0, ic1) = get<0>(ct).equal_range(md5_); 
channel_table_pr_view ctpv; 
while (ic0 != ic1) 
{ 
    ctpv.insert(&*ic0);  /// compiled error!
    ++ic0; 
} 

but it compiled error:
Error	1	error C2664: 'std::pair<_Ty1,_Ty2>
boost::multi_index::detail::ordered_index<KeyFromValue,Compare,SuperMeta,TagList,Category>::insert(channel
*const )' : cannot convert parameter 1 from 'const channel*' to 'channel
*const '.

Joaquin M Lopez Munoz wrote:
> 
> isjk escribió:
>> hi,
>>
>> now, I have two structures like this,
>>   
>> [...]
>>
>> typedef multi_index_container<
>>     const channel*,
>>     ordered_non_unique<
>>        key_from_key<
>>           BOOST_MULTI_INDEX_MEMBER(peer, const int, guid_),
>>           BOOST_MULTI_INDEX_MEMBER(channel, const peer*, pr_)
>>        >
>>     >
>>   
>>> channel_table_pr_view;
>>>     
>>
>> [...]
>>
>> channel_table_pr_view::iterator ictpv = ctpv.find(guid_);
>> if (ictpv != ctpv.end())
>> {
>>     ctpv.modify(ictpv, _Modify_prop()); // right or not?
>> }
>>
>> struct _Modify_prop{
>>     void operator()(channel& cl_)
>>     {
>>          cl_.prop = rand();
>>     }
>> };
>>
>>   
> 
> This is not correct: _Modify_prop is passed a reference to the element of
> channel_table_pr_view, which is a const channel*, so the right signature
> for _Modify_prop::operator() is
> 
>   struct _Modify_prop{
>       void operator()(const channel*& pcl_);
>   };
> 
> Due to the const qualifier you won't be able to do the modification, so 
> consider
> redefining channel_table_pr_view as holding pointers to non-const objects:
> 
>   typedef multi_index_container<
>     channel*,
>     ordered_non_unique<
>       ...
>   > channel_table_pr_view;
> 
> and making the necessary adjustments.
> 
> Joaquín M López Muñoz
> Telefónica, Investigación y Desarrollo
> _______________________________________________
> Boost-users mailing list
> Boost-users_at_[hidden]
> http://lists.boost.org/mailman/listinfo.cgi/boost-users
> 
> 

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