Re: [Boost-users] bind()ing only some arguments of a member function

From: Peter Dimov (pdimov_at_[hidden])
Date: 2006-02-13 18:28:16

Sean Rhea wrote:

> Hello,
>
> Can someone please tell me why this doesn't work?
>
>
> #include <boost/bind.hpp>
> #include <boost/function.hpp>
> #include <boost/shared_ptr.hpp>
>
> using namespace std;
> using namespace boost;
>
> struct MyClass {
>      int i;
>      void foo(int j){
>          printf("%d, %d\n", i, j);
>      }
>      function<void(int)> bar() {
>          return bind<void>(&MyClass::foo, this);
>      }
> };

Unlike some other libraries, bind does not automatically append incoming 
arguments to the call; if you say bind( f, 5 ), it calls f( 5 ), regardless 
of how many input arguments are supplied. If you want the first input 
argument to be passed to MyClass::foo, you need to mention it explicitly, 
using _1:

    bind( &MyClass::foo, this, _1 )