How to initialize static members?

I have to write a class with a static int member but I do not wish to initialize this member until I need to use it in one of my functions.


Let say i have for example:
private:
static int x;

I tried to initialize this by typing "int Classname::x=0; "in my function and it didn't work.

So how do I do this??

Thank you!

Code:

---

#include <iostream>


class X
{
  private:
  static int i;

  public:
  void set(int j) { i = j;}
  int get() {return i;}

};

int X::i;

int main(void)
{
  X x1, x2;
  x1.set(10);
  x2.set(20);
  std::cout <<"x1: " <<x1.get() <<std::endl;
  std::cout <<"x2: " <<x2.get() <<std::endl; 
 
  return(0);
}

/* output:

x1: 20
x2: 20

*/

---

so that initialization is never done within a function but just independently?

Thank you so much btw!

What is the purpose of this line: int X::i;

that line is used to initialize teh static member.

But i don't see why it is written there

The static member must be instantiated somewhere. It is only declared inside the class, but must be instantiated once and only once somewhere outside the class. If your class declaration is in a header file, you usually put the instantiation of static variables in the source file. In Hammer's example the variable is not explicitly intialized, although you could initialize it like this:

int X::i = 20;

>>In Hammer's example the variable is not explicitly intialized
To clarify, it is implicitly initialised to zero, just like any other static variable, hence I omitted an explicit initialising statement.