Question

If I have a functor like this…

class DoStuff {

  private:

    std::vector < int > numericStuff;

  public:

    explicit DoStuff (const std::vector <int> &newStuff) : numericStuff (newStuff) {};

    int operator () (void) {

       int ProcessedStuff = 0;

       //...Doing stuff

       return ProcessedStuff;

    };

};

…now, if I wanted to use it normally all I would have to do is…

//...Vector declared and populated somewhere else
DoStuff stuff (Vector);
int someNumber = stuff();

…and there you go. What I want to do is throw it into a boost::thread like this…

DoStuff stuff (Vector);
boost::thread (stuff);

…and then use it, but for the life of me I can’t find out how. Any help would be appreciated.

Answer 1

You can’t do this. To “return a value” from a thread, you have to use Futures.
Quoting from the above documentation:

When the packaged task is invoked, it invokes the contained function
in turn, and populates a future with the return value. This is an
answer to the perennial question: “how do I return a value from a
thread?”: package the function you wish to run as a
boost::packaged_task and pass the packaged task to the thread
constructor. The future retrieved from the packaged task can then be
used to obtain the return value. If the function throws an exception,
that is stored in the future in place of the return value.