Accessing main form from functions in other classes

I'm trying to draw a line on a form through a function which is in a class that I created inside another .h and .cpp file. But I cannot give it access to the main form or it's controls. Is there any way that I can pass the form into the functions of the class or a way that I can access the main form or maybe just a picturebox on the form in which I can draw too. And if so, how can I declare a temporary form / picturebox inside the class which I can then assign to the form / picturebox of the main form to?

PJ

This sounds like VB except for the references to .h and .cpp. In this instance you may want to make class A a friend of class B. I don't normally recommend this and normally using friend indicates to you that your class structure is seriously flawed, but there are certain times when a friend is the only way to get the job done. Usually those instances are when you want class A to manage all instances of class B, but you don't want the user to be able to explicitly instantiate class B. They must go through class A to instantiate class B. Of course then class A would need to be a singleton class to avoid more issues.

But since A and B do not have any prior knowledge of each other and are not derived from each other this is sometimes the only way.

Code:

---

class B;
 
class A
{
static friend class B;
static vector<B> BList;
public:
        A () {};
        static unsigned int CreateB(void)
        {
        B *temp=new B;
        BList.push_back(temp);
        ..set unique ID for new B
        return ID;
        }
        static B GetB(unsigned int _ID) {return BList[_ID];};
private:
  //Hide copy constructor to prevent misuse and/or improper implicit instantiation
  //Just in case somehow someone does get access - always assert as false
  //Fail in all cases
  A(A& obj) {ASSERT(false);};
};
 
class B
{
  private:
        B() {}
};

---

I coded this while sitting here so I'm fairly sure it doesn't work as shown. But it shows the general principle where a friend is pretty much the only way to get the job done.