Re: [Boost-users] Boost:multi-index Question on usage of project &modify_key

Subject: Re: [Boost-users] Boost:multi-index Question on usage of project &modify_key
From: joaquin_at_[hidden]
Date: 2009-01-15 02:30:06

Ramesh escribió:
> Hello.
>
> I am using projection technique & modify_key in one of my member functions:
>
> Assuming I have the following data in the container:
>
> ObjId      ObjIp               ObjIndex               pMyObj
> -------------------------------------------------------------------------------------
> ID1        10.10.1.2    	     1     		0x10239032
> ID2        10.10.1.3  	     2     		0x23423423
> ID3        10.10.1.4               3		0x23132423
>
> The member function 'UpdateKeyObjId' accepts the value on column 3 as
> key & changes the corresponding value
> for the field in Column 1.
>
> My code seems to work fine for all rows except the last row. When I
> use modify key on the last record, the app crashes at
> the highlighted line.  I am not sure if my usage of project &
> modify_key right, could someone please point out if there
> are any errors in the usage?
>   

Hello Ramesh,

At first sight your code appears correct. The only plausible way that I 
can figure out
the offending statement can crash:

  return MyContainer.get<0>().modify_key(ObjIdit, ll::_1 = param_ObjId);

happens if ObjIdit==MyContainer.end(). You can check this by placing an 
assertion
before that:

    typedef tMyObjMap::index<ObjIndex>::type tMyObjMapByIndex;
    tMyObjMapByIndex& ObjIndex_index = MyContainer.get<ObjIndex>();

    tMyObjMap::index_iterator<ObjIndex>::type it =
    ObjIndex_index.find(param_ObjIndex);

    assert(it!=ObjIndex_index.end());

    ...

If the assertion fails then there's simply no element with the given 
param_ObjIndex,
which I guess you can trace back to some problem elsewhere in your program.

HTH,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo