Re: [Boost-users] Using Boost::Bind

Subject: Re: [Boost-users] Using Boost::Bind
From: David McCallum (dmccallum9_at_[hidden])
Date: 2011-06-29 12:28:25

I should clarify, this is what I want to achieve:

boost::function<void (DBuffer&)> singleHandler;

void addHandler(boost::function<void (DBuffer&)> newHandler)
{
    singleHandler = newHandler;
}

The problem is that I don't know how to call boost::bind with a
DBuffer parameter, where DBuffer is one of my own classes.

> You will want to learn a bit more about Boost.Bind. You can bind your
> pointer or variable at the bind call. Parameters at the time of bind are
> copied by value. If you need a reference use the boost::ref wrapper.

> Expanding your example:

> void DClient::resolveHandler( const boost::system::error_code& error,
>                                int value );
> ...
> int special_number = 42;
>
> hostResolver->async_resolve( *nameQuery,
>                               boost::bind(&DClient::resolveHandler, this,
>                                           boost::asio::placeholders::error,
>                                           special_number ) );
>
> -------------------
>
> In the above, when the handler is invoked it will pass the error value
> (via the placeholder) and the value of special_number during the bind...
> which is 42.

If I understand you correctly, then in the following code:

void DClient::resolveHandler(int param)
{
    ....
}

boost::function<void (int)> functionPtr;
int tempInt = 12;

myHandler = boost::bind(&DClient::resolveHandler, this, tempInt);
myHandler(67);

The final line will call resolveHandler with a parameter of 12, rather
than 67? Surely that can't be right?