asio 0.1.5 | Main Page | Class Index | Member Index | Tutorial |
#include <iostream> #include "boost/bind.hpp" #include "asio.hpp"
Step 1. Instead of defining a free function print
as the callback handler, as we did in the earlier tutorial programs, we now define a class called printer
.
class printer { public:
Step 2. The constructor of this class will take a reference to the demuxer object and use it when initialising the timer_
member. The counter used to shut down the program is now also a member of the class.
printer(asio::demuxer& d) : timer_(d, asio::timer::from_now, 1), count_(0) {
Step 3. The boost::bind
function works just as well with class member functions as with free functions. Since all non-static class member functions have an implicit this
parameter, we need to bind this
to the function. As in Part 3, boost::bind
converts our callback handler (now a member function) into a function object that matches the signature void()
.
timer_.async_wait(boost::bind(&printer::print, this));
}
Step 4. In the class destructor we will print out the final value of the counter.
~printer() { std::cout << "Final count is " << count_ << "\n"; }
Step 5. The print
member function is very similar to the print
function from Part 3, except that it now operates on the class data members instead of having the timer and counter passed in as parameters.
void print() { if (count_ < 5) { std::cout << count_ << "\n"; ++count_; timer_.set(asio::timer::from_existing, 1); timer_.async_wait(boost::bind(&printer::print, this)); } } private: asio::timer timer_; int count_; };
Step 6. The main
function is much simpler than before, as it now declares a local printer
object before running the demuxer as normal.
int main() { asio::demuxer d; printer p(d); d.run(); return 0; }
See the Source listing for Tutorial Part 4
Return to the Tutorial Index
Go back to Tutorial Part 3 - Binding arguments to a handler