Passing parameter to boost::thread no overloaded f

问题:

From the boost::thread documentation it seems that I can pass parameters to the thread function by doing this:

boost::thread* myThread = new boost::thread(callbackFunc, param);

However, when I do this the compiler complains that

no overloaded function takes 2 arguments

My code:

#include <boost/thread/thread.hpp>
void Game::playSound(sf::Sound* s) {
    boost::thread soundThread(playSoundTask, s);
    soundThread.join();
}

void Game::playSoundTask(sf::Sound* s) {
    // do things
}

I am using the copy of boost that came with Ogre3d, which I suppose could be very old. Interestingly, though, I took a look at thread.hpp and it does have the templates for constructors with 2 or more parameters.

回答1:

The problem is that member functions take an implicit first parameter Type*, where Type is the type of the class. This is the mechanism by which member functions get called on instances of types, and means you have to pass an extra parameter to the boost::thread constructor. You also have to pass the address of the member function as &ClassName::functionName.

I have made a small compiling and running example that I hope illustrates the use:

#include <boost/thread.hpp>
#include <iostream>

struct Foo
{
  void foo(int i) 
  {
    std::cout << "foo(" << i << ")\n";
  }
  void bar()
  {
    int i = 42;
    boost::thread t(&Foo::foo, this, i);
    t.join();
  }
};

int main()
{
  Foo f;
  f.bar();
}