Generalize the argument passed to boost::bind - c++

Question

I am trying to write a generic struct MyCounter which uses boost::bind . What I am trying to do is to write MyCounter such a way that by changing its template argument type, I could bind to different methods. I was under the impression that if I pass something like MyThread::send as a template argument, I will be able to use it directly in bind(). Apparently I was wrong. Could you kindly help me with the alternatives? Thank you
#include <boost/bind.hpp>
#include <boost/function.hpp>
#include <boost/shared_ptr.hpp>
#include <boost/make_shared.hpp>
#include <vector>
#include <utility>
struct MyThread //simplified
{
void send1()
{
std::cout << "In Send1\n";
}
void send2()
{
std::cout << "In Send2\n";
}
};
struct Job //ignore me
{
Job(const unsigned int interval)
: _tChk(0)
, _tInterval(interval)
{}
void operator()(unsigned long nowSec)
{
if (nowSec > _tChk)
{
_functor();
_tChk += nowSec + _tInterval;
}
}
private:
unsigned long _tChk;
const unsigned int _tInterval;
protected:
boost::function<void()> _functor;
};
struct JobInvoker //ignore me
{
typedef boost::shared_ptr<Job> JobPtr;
JobInvoker(MyThread &myThread)
: _myThread(myThread)
{}
template<typename JOB>
void addJob(const unsigned int interval)
{
JobPtr job = boost::make_shared<JOB>(interval, _myThread);
_jobs.push_back(job);
}
void operator() (JobPtr job)
{
(*job)(_now.tv_sec);
}
void invoke(timeval now)
{
_now = now;
std::for_each(_jobs.begin(), _jobs.end(), *this);
}
timeval _now;
std::vector<JobPtr> _jobs;
MyThread &_myThread;
};
//my struggle
template<typename F>
struct MyCounter : public Job
{
MyCounter(const unsigned int interval, MyThread &myThread)
: Job(interval)
{
_functor = boost::bind(&F, &myThread); //<-- Error
}
};
int main()
{
MyThread t;
JobInvoker jobInvoker(t);
jobInvoker.addJob<MyCounter<MyThread::send1> >(2); //<-- Error
jobInvoker.addJob<MyCounter<MyThread::send2> >(2); //<-- Error
timeval now;//...
jobInvoker.invoke(timeval now)
return 0;
}
UPDATE:
compiled with:
g++ boost_f.cpp -lboost_system
we get the following errors:
boost_f.cpp: In constructor ‘MyCounter<F>::MyCounter(unsigned int, MyThread&)’:
boost_f.cpp:81:34: error: expected primary-expression before ‘,’ token
_functor = boost::bind(&F, &myThread); //<-- Error
^
boost_f.cpp: In function ‘int main()’:
boost_f.cpp:89:46: error: type/value mismatch at argument 1 in template parameter list for ‘template<class F> struct MyCounter’
jobInvoker.addJob<MyCounter<MyThread::send1> >(2); //<-- Error
^
boost_f.cpp:89:46: error: expected a type, got ‘MyThread::send1’
boost_f.cpp:89:51: error: no matching function for call to ‘JobInvoker::addJob(int)’
jobInvoker.addJob<MyCounter<MyThread::send1> >(2); //<-- Error
^
boost_f.cpp:89:51: note: candidate is:
boost_f.cpp:52:10: note: template<class JOB> void JobInvoker::addJob(unsigned int)
void addJob(const unsigned int interval)
^
boost_f.cpp:52:10: note: template argument deduction/substitution failed:
boost_f.cpp:89:51: error: template argument 1 is invalid
jobInvoker.addJob<MyCounter<MyThread::send1> >(2); //<-- Error
^
boost_f.cpp:90:46: error: type/value mismatch at argument 1 in template parameter list for ‘template<class F> struct MyCounter’
jobInvoker.addJob<MyCounter<MyThread::send2> >(2); //<-- Error
^
boost_f.cpp:90:46: error: expected a type, got ‘MyThread::send2’
boost_f.cpp:90:51: error: no matching function for call to ‘JobInvoker::addJob(int)’
jobInvoker.addJob<MyCounter<MyThread::send2> >(2); //<-- Error
^
boost_f.cpp:90:51: note: candidate is:
boost_f.cpp:52:10: note: template<class JOB> void JobInvoker::addJob(unsigned int)
void addJob(const unsigned int interval)
^
boost_f.cpp:52:10: note: template argument deduction/substitution failed:
boost_f.cpp:90:51: error: template argument 1 is invalid
jobInvoker.addJob<MyCounter<MyThread::send2> >(2); //<-- Error
^
boost_f.cpp:92:29: error: expected primary-expression before ‘now’
jobInvoker.invoke(timeval now)

Answer 1

Like the error says, a member function isn't a type, so it can't be used for a template type parameter.
Instead, you need to use a non-type parameter:
template<void(MyThread::*F)()>
struct MyCounter : public Job
{
MyCounter(const unsigned int interval, MyThread &myThread)
: Job(interval)
{
_functor = boost::bind(F, &myThread);
}
};
Live Example
Note that I made F a pointer to a member function of MyThread instead of a typename.