Re: Return class record std::list

From:
"Alf P. Steinbach" <alfps@start.no>
Newsgroups:
comp.lang.c++
Date:
Sun, 13 Sep 2009 02:21:19 +0200
Message-ID:
<h8hdu3$29t$1@news.eternal-september.org>
* XX:

Please help, and thanks.....
How to compare iterator with class [s==skip_share].
Return iterator as a class record [return s;].

error C2678: binary '==' : no operator found which takes a left-hand operand
of type 'std::list<_Ty>::_Iterator<_Secure_validation>' (or there is no
acceptable conversion)
error C2440: 'return' : cannot convert from
'std::list<_Ty>::_Iterator<_Secure_validation>' to 'cShare *'

#include <list>
using namespace std;

class cShare {
private:
 int connection_id;
public:
 cShare(int _connection_id);
 int Get_connection_id(void) const { return connection_id; };
};


You're using a lot of prefixes, "c...", "_...", "Get_". They serve no useful
purpose and reduce readability. On the other hand, a prefix on the data member
name would be useful, but is lacking.

cShare::cShare(int _connection_id)
{
 connection_id = _connection_id;
}


When there's no special reason to use assignment, consider a memory initialiser
list:

   cShare::cShare( int id )
       : connection_id( id )
   {}

class cShares
{
private:
 list<cShare> cshares;
public:
 cShares();
 virtual ~cShares();
 cShare *cShares::SearchCon(int connection_id, cShare *skip_share);
};


For this functionality, if cShare in actuality holds more information than just
an id then you'd be better off using a std::map.

If it just holds an id then the functionality amounts to a std::set.

cShares::cShares()
{
}

cShares::~cShares()
{
}

cShare *cShares::SearchCon(int connection_id, cShare *skip_share)
{
 list<cShare>::const_iterator s;
 for (s = cshares.begin(); s != cshares.end(); ++s) {
  if(s==skip_share) continue;


A list iterator is not a pointer to a list element.

You might check the id:

    if(
        skip_share != 0 &&
        s->Get_connection_id() == skip_share->Get_connection_id()
        )

If skip_share can't be 0 then you should pass it by reference, not as a pointer.

  if(s->Get_connection_id()==connection_id) return s;


Ditto: 's' is a list iterator, not a pointer to cShare.

You can do

     return &*s;

 }
 return NULL;
}


tShares!, & hth.,

- Alf

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