#include <iostream>
#include <boost/asio.hpp>
#include <functional>
class printer
{
public:
printer(boost::asio::io_context& io)
: timer_(io, boost::asio::chrono::seconds(1))
{
timer_.async_wait(std::bind(&printer::print, this));
// timer_.async_wait([this]() {
// print();
// });
}
void print()
{
std::cout << "hello world" << std::endl;
}
private:
boost::asio::steady_timer timer_;
};
int main()
{
boost::asio::io_context io;
printer p(io);
io.run();
return 0;
}
I tried to replace the following line:
timer_.async_wait(std::bind(&printer::print, this));
with
timer_.async_wait([this]() {
print();
});
But it failed and the compiler reports the following errors:
main.cpp: In constructor 'printer::printer(boost::asio::io_context&)':
main.cpp:12:22: error: no matching function for call to 'boost::asio::basic_waitable_timer<std::chrono::_V2::steady_clock>::async_wait(printer::printer(boost::asio::io_context&)::<lambda()>)'
12 | timer_.async_wait([this]() {
| ~~~~~~~~~~~~~~~~~^~~~~~~~~~~
13 | print();
| ~~~~~~~~
14 | });
| ~~
Question> What is the correct way to rewrite the std::bind with lambda expression?
Thank you
Your lambda doesn't have the required signature.
Based the boost documentation, the callback takes a const boost::system::error_code& argument. std::bind lets you be a bit looser in the function signature (Why std::bind can be assigned to argument-mismatched std::function?), but lambdas need to be an exact match.
The following code seems to work for me
timer_.async_wait([this](auto const &ec) {
print();
});