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I know static class member function don't need to be instantiated. But, since class member functions' manipulation are always based on its' own member variables, why we still use the static member functions? can someone tell me by some detail examples? Thanks in advance.

P.S. I am writing a program that in one class member function create two threads, so that I need to pass the thread callback function address to when create the two threads. I want the thread callback function also be the same class's member function. According to some references, if a callback function is a class's member, it should be static. There comes the question: in the static callback, I can't call other non-static function in the same class, and can't modify it's non-static member variables. (English is my secondary language, so I'am not good at it. hope some help me describe it more succinctly:-)

Bruce Yang
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    Your question is unclear. Some member functions' actions are *not* based on the values of member variables; such functions can be `static`. – Beta Nov 15 '13 at 05:38

1 Answers1

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I will just give you an example. If you want to calculate how many instances you have declared about your class, you may have a static member like 

int instance_count;

and in the class constructor you can add the instance_count like:

instance_count++;

and in your destructor :

instance_count--;

As a result, you can get how many instances you have currently in your program.

yanchong
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