Initialize C++ Thread and Run Later

Question

I'm assuming there's an easy answer to this question. I want to first define a thread as a member variable of a class, and then later start this thread in a different function.

For example:

The header file:

#include<thread>
class Foo{
public:
   void threaded_method();
   void start_thread();
private:
   std::thread m_thread;      
};

Cpp file:

void Foo::start_thread(){
    m_thread = std::thread(threaded_method);
}

Although the above does not work, thoughts?

As far as I can see from the docs, that _should_ work. What exactly do you mean by "does not work"? Do you get an error message? — celticminstrel, Jul 09 '15 at 15:29
@JoachimPileborg - threads are supposed to be move-assignable. — celticminstrel, Jul 09 '15 at 15:31
`threaded_method` is a member function, that can't be passed to the thread this way. Assigning `m_thread` from another instance is perfectly fine, and should do what you want. — πάντα ῥεῖ, Jul 09 '15 at 15:32

score 11 · Accepted Answer · answered Jul 09 '15 at 15:32

11

To pass a member function to a thread, you must also pass an instance on which to execute that function.

void Foo::start_thread(){
    m_thread = std::thread(&Foo::threaded_method, this);
}

answered Jul 09 '15 at 15:32

François Moisan

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12

Thanks! Realized the answer soon after I posted the question. – Lucas Jul 09 '15 at 15:57

score 0 · Answer 2 · edited May 23 '17 at 12:08

0

Found a good example in these pages:

I forgot to pass in a valid reference to the member function.

void Foo::start_thread(){
    m_thread = std::thread(&Foo::threaded_method, this);
}

Should work. Love finding the answer right after I post a question...

edited May 23 '17 at 12:08

Community

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answered Jul 09 '15 at 15:57

Lucas

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I used to do that too. From now, resist the temptation to post a question, first search it thoroughly on google as well as SO and then spend another minute reevaluating it inside your head. You'll answer most of your questions easily. – Abhinav Gauniyal Jul 09 '15 at 16:26

score 0 · Answer 3 · answered Apr 23 '18 at 16:27

0

You might also simply change your architecture. For example, have a list and which would contain the functions you want to perform. Then multithread your way through all the functions you want to run.

answered Apr 23 '18 at 16:27

FunkMasterP

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Initialize C++ Thread and Run Later

3 Answers3