Access class variable from std::thread - c++

Question

I have the following class which kicks off a new std::thread. I now want the thread to access a member variable of the class. So far I cannot work out how to do this.
In my MyThread function I want to check m_Continue.
I have tried passing in 'this' when the thread is created but I get an error:
Error 1 error C2197: 'void (__cdecl *)(void)' : too many arguments for call c:\program files (x86)\microsoft visual studio 11.0\vc\include\functional 1152 1 MyProject.
class SingletonClass
{
public:
SingletonClass();
virtual ~SingletonClass(){};
static SingletonClass& Instance();
void DoSomething();
private:
static void MyThread();
std::thread* m_Thread;
bool m_Continue;
};
SingletonClass::SingletonClass()
{
m_Continue = true;
m_Thread= new std::thread(MyThread, this);
}
void SingletonClass::MyThread()
{
while(this->m_Continue )
{
// do something
}
}
void SingletonClass::DoSomething()
{
m_Continue = false;
}
SingletonClass& SingletonClass::Instance()
{
static SingletonClass _instance;
return _instance;
}
int _tmain(int argc, _TCHAR* argv[])
{
SingletonClass& singleton = SingletonClass::Instance();
singleton.DoSomething();
return 0;
}
How can I do this??

Answer 1

If you want to access this from within the thread function, then it shouldn't be static:
void MyThread();
Now you can simply pass this as the second thread constructor argument, as you tried; but, being a non-static member, you'll need to qualify its name:
m_Thread= new std::thread(&SingletonClass::MyThread, this);
Alternatively, you might find a lambda easier to read:
m_Thread= new std::thread([this]{MyThread();});
But you shouldn't muck around with pointers and new like that; make the member variable a thread object and initialise it in the initialiser list:
SingletonClass::SingletonClass() :
m_Continue(true), m_Thread([this]{MyThread();})
{}
making sure to declare m_Thread after any other members that it accesses; and make sure you stop and join the thread in the destructor, or earlier.
Finally, m_Continue should be std::atomic<bool> in order to set it on one thread and read it on another with well-defined behaviour.

Answer 2

Replace
static void MyThread();
with
void MyThread();
as
this cannot be access within static method.

Answer 3

You can access the member variable if it is public or you may make have a method like "bool shallContinue()" which returns m_Continue.
Now how do you do this. Check the below modified snippet:
static void SingletonClass::MyThread(SingleTonClass *arg)
{
while(arg->shallContinue() )
{
// do something
}
}
Below a complete example:
#include <iostream>
#include <thread>
#include <unistd.h>
using namespace std;
class A
{
public:
A(int x) : a(x)
{
thr = new thread(myThread, this);
}
static void myThread(A *arg)
{
arg->show();
}
void show()
{
cout << a << endl;
}
private:
int a;
thread *thr;
};
int main()
{
A a(1);
sleep(2);
return 0;
}