Calling methods from other class objects, and vice versa

[one0paulie]

Hello, I have a query regarding the possibilities of a class method (class A) calling the method of another class (class B), with a method of that class (B) calling a method of the first class (A). For example, take the following (which won't compile as is, but please see below):

class A
{
public:
  vector<int> a_test;

  A_method_1 (int a)
  {
    //doing something simple to a_test...
    a_test.push_back(a);
  }

  A_method_2 ()
  {
    //do something else, then call a method from class B...
    B_method_1(2);
  }
};


class B
{
public:
  vector<int> b_test;

  B_method_1 (int b)
  {
    //doing something simple to b_test...
    b_test.push_back(b);
  }

  B_method_2 ()
  {
    //do something else, then call a method from class A...
    A_method_1(1);
  }
};

Basically, the aim is for a method in class A (or rather object _A) to modify some data structure in class B (or rather object _B) at some point, and then for a method in class B to modify some structure in class A at some later point. There are multiple instantiations of both classes A and B, so what I have done is the following (using the class A method for example):

//redefine A_method_2 to take an argument of type class B by reference
A_method_2 (B &b)
{
  //do stuff
  b.B_method_1(2);
}
//and then the vice versa for the definition of B_method_2... 

My query is: is there a more preferable/logical/efficient means of doing this? For me, classes A and B
are functionally very different (apart from this cross-over!), and so straightforward inheritance won't work here.

Many thanks in advance for any feedback/suggestions you may have.

Paul

[firedraco]

Nope, that would pretty much be the only way to do it.

However, if the classes are regularly modifying a specific instance of the other class (i.e. each class A has a specific class B that it will always modify), then you could have class A/B contain a pointer/reference (depending on when you set/need it) to the other class.

[onur]

Why does A_method_2 has to be a member of class A?

Have you considered using a simple function instead of a method?
Even if you need access to both objects this may be a better alternative:

void method_2(A& a, B& b, int i, int j)
{
  a.A_method_1 (i);
  b.B_method_1 (j);
  //...
}

I further prefer to add a method to the class it modifies.
So if you need data from class A but modify class B, add the method to class B.

If you can describe what's going on in these methods maybe I can give a more precise hint.

[one0paulie]

Thank you both for your very quick and helpful replies!

firedraco:
That's interesting, may use that (even though it just changes the organisation rather than the way its done, as far as I understand) - each instantiation of class A is 'paired' with an instantiation of class B in the sense that object_A1 always interacts with object_B1, object_A2 with object_B2, etc...

onur:
I have A_method_2 as a member of class A since it performs computation within the members of class A, with the result being used on the call to the method in class B. If I understand your suggestion correctly, then it will be useful in certain circumstances, but I don't think here. Hmm, will have a think about it though...

One issue that may become relevant (but I don't think to this example in itself) is that class B (for example) is a 'stub/dummy' for a far more complex class written by someone else. Therefore, I want to be able to minimise the modifications required in that class to interact with my class A. The encapsulation thing is important here :-) Thanks again.

[webJose]

It doesn't matter how far apart you think 2 classes are: You will always find common ground if you look hard enough.

With the above in mind, think about interfaces (in the COM or .Net way). Interfaces excel at providing a contract between 2 otherwise unrelated classes. Examples: A building and a car. Two quite unrelated objects, but in the context of inventory or accounting, you can see each as an asset, with a nominal value, etc. By creating the Car class and the Building class so that they both implement the pure virtual class IAsset, you have a common ground to work with the two.

So find the common ground here and define a pure virtual class that satisfies the scenario.