0
class foo
{
    bar b;

    someFunction()
    {
        b.alphaObj->someFunctionOfAlpha();
    }
};


class bar
{
    friend class foo;
    // many more friends

private:
    alpha *alphaObj;
};

How do I remove the friend dependency without exposing the private members with getters and setters. I understand friend classes could help in enhancing encapsulation but there are a lot of friend classes defined in my class exposing the private members to all. Hence I am thinking of a better approach and any help is appreciated.

abhilash anand
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    Requiring a lot of friends indicates a set of poorly encapsulated classes - Why do so many classes require access to class bar? – Tom Dec 10 '19 at 09:41
  • We are dealing with legacy code here and that's how it is. We are thinking of refactoring now with a better design – abhilash anand Dec 10 '19 at 09:44
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    The example here feels a bit too generic to be useful. Generally `someFunctionOfAlpha` wants to be moved to some other class where it can be made public. It could potentially be a wrapper that say `bar` creates, or become a member of `bar` itself. Another option is to pass a callback function and call that, instead of calling whatever it is directly. – Fire Lancer Dec 10 '19 at 09:44

1 Answers1

1

Independent of your friend issue, being required to write this

b.alphaObj->someFunctionOfAlpha();

is not the best design. You should rather call (*):

b.someFunctionOfAlpha();

Now it is also obvious how to remove the friends:

class bar
{
public:
    void someFunctionOfAlpha() { alphaObj->someFunctionOfAlpha(); }

private:
    alpha *alphaObj;
};

(*) This guideline has a name, I just cannot find it at the moment. In general, calling a method should be like: "Do that!". Calling a method should not be like "Show me your internals so I can do what I want".

463035818_is_not_an_ai
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  • Thank you. This answer shows a valid point but does not answer the question. Hence not marking as correct – abhilash anand Dec 11 '19 at 03:56
  • @abhilashanand why does it not answer the question? I show you how you can resolve the need for `friend` – 463035818_is_not_an_ai Dec 11 '19 at 08:48
  • Yes. But this exposes the inner features of alpha class indirectly by making it public. I have mentioned it as a constraint to not expose the inner functionalities by means of getters and setters – abhilash anand Dec 11 '19 at 10:10
  • We had a discussion and this was pretty good and hence marked as correct. Another suggestion was the make the member public and make it a const such that it cannot be modified. If there are a lot of variables then your suggestion could result in a lot of code. Thanks for your effort – abhilash anand Dec 11 '19 at 10:40
  • I think you are referring to "Law of Demeter" above :) – abhilash anand Dec 11 '19 at 10:54
  • @abhilashanand yes you mentioned no getters and setters and I tried to give some hint that getters and setters is not what makes OOD. Anyhow I am not using getters/setters. For alternatives and pros/cons you should have made the requirements more clear in the question. Yes indeed it is Demeters Law, will edit that in – 463035818_is_not_an_ai Dec 11 '19 at 12:17