CODEWITHSUNDEEP
c++static
A. Vieira
A. Vieira

Reputation: 1281

How to correctly link static class

Suppose I have a class that only has static members:

OnlyMaths.h:

#include "2DData.h"

class OnlyMaths{
public:
  static double average(2DData* a); // Will call 2DData's functions
  //... more static functions
private:
  OnlyMaths() {} // Non-instantiable class
};

And that 2DData is a class that uses OnlyMaths:

2DData.h:

#include "OnlyMaths.h"

class 2DData{
public:
  2DData(double x, double y);
  double average() {
    return OnlyMaths::average(this); // Uses static function
  }
};

Both classes need to know each other (and their methods) in order to perform their functions, but, as I wrote it, there is a circular inclusion and it wont compile.

How do I make a "static" class like OnlyMaths know other classes it needs in it's functions and have it's static functions called anywhere? Surely there is a correct way of doing this.

Note: Please assume that all *.h files are define protected with #ifndef ... as usual.

EDIT:

Some circular dependencies questions, like this, are given solutions that revolve around forward declaration. In this case this is not a possibility, as not only both classes need to know each other but also they need to know each other's functions.

By the difficulty in finding a simple solution I'm starting to think that the way I'm going about the problem may not be right, so let me clarify my goal:

The goal is to have a file OnlyMaths.h contain all the functions that do mathematics operations on all data types I have in my project. This functions can be called anywhere in the project, sometimes even inside the classes OnlyMath's operates on.

Upvotes: 0

Views: 79

Answers (1)

M.L.
M.L.

Reputation: 738

One solution is to include 2DData.h in OnlyMaths.cpp:

OnlyMaths.h :

class 2DData; // Declaration only.
class OnlyMaths{
public:
  static double average(2DData* a); // Will call 2DData's functions
  //... more static functions
private:
  OnlyMaths() {} // Non-instantiable class
};

OnlyMaths.cpp :

#include <OnlyMaths.h>
#include <2DData.h>
double OnlyMaths::average(2DData* a)
{
    a->method();
}

This way, 2DData's functions are available for any OnlyMaths's functions and vice-versa, without circular dependencies.

Upvotes: 2

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