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std::mem_fun + boost::shared_ptr ???

Started by gimp Aug 8, 2002 at 4:48 AM 4 replies 3.1k views

Original Post

Aug 8, 2002 at 4:48 AM

How would I write the syntax for this: std::for_each(m_PersistentEvents.begin(), m_PersistentEvents.end(), std::mem_fun(&CGameEvent::Execute)); Where m_PersistentEvents no longer is filled with pointers, but smart pointers? Error : ''std::mem_fun_t::operator`()'''' : cannot convert parameter 1 from ''boost::shared_ptr'' to ''CGameEvent *'' ..or is this a case of ''not unless you modify boost''? Many thanks, Chris Brodie http:\\fourth.flipcode.com

dalleboy

Aug 8, 2002 at 6:47 AM

Use boost::mem_fn instead of std::mem_fun.

  

#include <vector>

#include <algorithm>

#include <boost/shared_ptr.hpp>

#include <boost/mem_fn.hpp>

class GameEvent
{
public:
   void Execute()
   {
   }
};

int main()
{
   std::vector<boost::shared_ptr<GameEvent> > oVector;
   oVector.push_back(boost::shared_ptr<GameEvent>(new GameEvent()));
   std::for_each(oVector.begin(), oVector.end(), boost::mem_fn(&GameEvent::Execute));

	return 0;
}

gimp

Aug 9, 2002 at 4:34 AM

Excellent advice. Thankyou. I appreciate the compilable example as well. Thanks.

Chris Brodie
http:\\fourth.flipcode.com

Fruny

Aug 9, 2002 at 12:57 PM

Or use boost::bind for more flexibility,

std::for_each(oVector.begin(), oVector.end(), boost::mem_fn(&GameEvent::Execute));

becomes

std::for_each(oVector.begin(), oVector.end(), boost::bind(&GameEvent::Execute, _1));

with _1 representing the first parameter that for_each passes to the functor (here, the this pointer).

I like boost::bind better, because it covers all possible combinations (member functions, member _variables_, regular functions ...).

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Kylotan

Aug 9, 2002 at 10:01 PM

sark

Aug 9, 2002 at 10:06 PM

Im with fruny on this one. boost::bind rocks. The _1 _2 substitution stuff may look strange at first but you get used to it.

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