循环依赖

Question

I have a class called Point and an other namespace containing a tree class. this tree is a balanced binary search tree, and uses the function compare to compare its keys and puts them in the right place. My tree contains Point s, and for each point I have to know which tree it belongs to, so I tried to add a pointer to the tree in my Point class like this:

class Point{
   public:
   double x, y;
   std::set<std::multiset<Point,Tree::compare()>*>s; //Tree is the name of the namespace
// some other data
}

My problem is that since my tree uses Point.h (because it stores Point s) I cant add LayerThree.h to my it so I cant use Tree::compare() in my Point.h . I tried to add a new file like cmp.h and put my compare function in it, But It did not help. What should I do?

EDIT: I can not put both my tree and my Point class together in the same file because there are other files that needs to include Point.h

Answer 1

As Jepessen mentioned already you need forward declaration. Here is an example:

Class A depends on class B AND class B depends on class A, use forward declaration like this:

In Class "Bh":

#include "A.h"

class B
{
   //Do stuff
};

And in Class "Ah":

 // Forward declaration of class B, this tells the compiler to not worry about 
 // class B as somewhere later in compilation class B will be declared
class B;

class A
{
   //Do stuff
};