Weird behavihor when calling thread through class member function with another member. CPP

Question

I tried the next code:

class JustClass
{
public:
    void JustFunc()
    {
        std::thread t(this->JustThread);
        t.detach();
    }

    void JustThread()
    {

    }

private:

};

It should not do any problems. I just call a function of my object to act like a thread. But I get the next error fot this:

But if Im doing that:

class JustClass
{
public:
    void JustFunc()
    {
        std::thread t(this->JustThread, 5);
        t.detach();
    }

    void JustThread(int just_var)
    {

    }

private:

};

Then now I get this Eroor:

Error   2   error C3867: 'JustClass::JustThread': function call missing argument list; use '&JustClass::JustThread' to create a pointer to member   c:\users\micha\onedrive\מסמכים\visual studio 2013\projects\project2\project2\source.cpp 58  1   Project2

Why is that weird behavior?

Answer 1

You pass member function pointers like this:

class JustClass
{
public:
    void JustFunc()
    {
        std::thread t(&JustClass::JustThread, this);
        t.detach();
    }
    void JustThread() {}
private:
};

For your second variation:

class JustClass
{
public:
    void JustFunc()
    {
        std::thread t(&JustClass::JustThread, this, 5);
        t.detach();
}
void JustThread(int just_var){}

---

If the function is overloaded, you will need to select which overload. See Jonathan Wakely's Answer to a related question. Also read this FAQ about pointers to member functions.