| Home | Libraries | People | FAQ | More

### Resolve handler requirements

A resolve handler must meet the requirements for a handler. A value `h` of a resolve handler class should work correctly in the expression `h(ec, i)`, where `ec` is an lvalue of type `const error_code` and `i` is an lvalue of type `const ip::basic_resolver_iterator<InternetProtocol>`. `InternetProtocol` is the template parameter of the `resolver_service` which is used to initiate the asynchronous operation.

##### Examples

A free function as a resolve handler:

    void resolve_handler(
        const boost::system::error_code& ec,
        boost::asio::ip::tcp::resolver::iterator iterator)
    {
      ...
    }

A resolve handler function object:

    struct resolve_handler
    {
      ...
      void operator()(
          const boost::system::error_code& ec,
          boost::asio::ip::tcp::resolver::iterator iterator)
      {
        ...
      }
      ...
    };

A non-static class member function adapted to a resolve handler using `bind()`:

    void my_class::resolve_handler(
        const boost::system::error_code& ec,
        boost::asio::ip::tcp::resolver::iterator iterator)
    {
      ...
    }
    ...
    resolver.async_resolve(...,
        boost::bind(&my_class::resolve_handler,
          this, boost::asio::placeholders::error,
          boost::asio::placeholders::iterator));