Using find_if and boost::bind with a set of shared_pointers

Question

I have a vector of shared_ptr, I want to combine boost shared_ptr and bind together.

My question is very similar to this, except that instead of "&MyClass::ReferenceFn" I would like to call "&Element::Fn".

Here is a similar piece of code:

typedef boost::shared_ptr< Vertex > vertex_ptr; 
std::set<vertex_ptr> vertices;

void B::convert()
{
...
if( std::find_if(boost::make_indirect_iterator(vertices.begin()), 
                 boost::make_indirect_iterator(vertices.end() ),  boost::bind( &Vertex::id, boost::ref(*this), _1 ) == (*it)->id() ) == vertices.end() )
}

here is the error:

no matching function for call to ‘bind(<unresolved overloaded function type>, const boost::reference_wrapper<B>, boost::arg<1>&)’

NOTE: I am limited to use the C++03.

@PiotrSkotnicki, the error is that it take (this keyword) as this pointer of class B — H'H
– H'H, Commented Mar 23, 2016 at 16:04
then perpahs you want boost::bind(&Vertex::id, _1) == (*it)->id()), or, boost::bind(static_cast<int(Vertex::*)()>(&Vertex::id), _1) == (*it)->id()) (where int is the return type of id) — Piotr Skotnicki
– Piotr Skotnicki, Commented Mar 23, 2016 at 16:05
thank you very much, if you provide you comment as an answer I will choose it as best solution. and Also will you please explain me what star means in "(Vertex::*) ? — H'H
– H'H, Commented Mar 25, 2016 at 16:42

Piotr Skotnicki · Accepted Answer · 2016-03-25 16:50:42Z

To call a member function for each object stored in a collection, you need to use a placeholder as the first bound argument of the boost::bind:

boost::bind(&Vertex::id, _1) == (*it)->id())
//                       ~^~

This way, each argument a, will be bound to a member function pointer, and called as (a.*&Vertex::id)().

However, seeing that the error message says unresolved overloaded function type, it draws a conclusion that your class Vertex can have multiple overloads of member function id. As such, the compiler is unable to tell which one it should pass as the argument of boost::bind. To solve this, use an explicit cast to a member function pointer (the asterisk after colon indicates it's a pointer to a member):

boost::bind(static_cast<int(Vertex::*)()const>(&Vertex::id), _1) == (*it)->id())
//                      ~~~~~~~~~~~~~~~~~~~~^

In the case class Vertex has multiple overloads, say:

int id() const { return 0; }
void id(int i) { }

you will use the first one for binding.

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