Thread: storing references

Hello

Lets say I have the following data structure:

Code:

class object {
public:
  void some_function();
  std::string get_something();
  void set_something();
private:
  //data
};

class main {
public:
  main() : m_subclass(*this) { }
  const object& get_object() { return m_object; }

private:
  object m_object;
  subclass m_subclass;
};

class subclass {
public:
  subclass(main &obj) : m_object(obj.get_object()) { }

private: 
 object &m_object;
};

This will give an error because object in subclass is not const.

I've been told that its right to return references by const, but in that case I would have to store it in subclass as const object.. Do you guys store references by const / non-const or does it depend on situation?

Thanks a lot for help!

Originally Posted by l2u

I've been told that its right to return references by const, but in that case I would have to store it in subclass as const object.. Do you guys store references by const / non-const or does it depend on situation?

I only store a reference as non-const if I actually intend to modify it. Obviously there are situations where you can't use const, but the basic rule is to make it const unless that is impossible.

Originally Posted by brewbuck

I only store a reference as non-const if I actually intend to modify it. Obviously there are situations where you can't use const, but the basic rule is to make it const unless that is impossible.

Does having const object means I cannot call set_something() function by the const object reference?

Originally Posted by l2u

Does having const object means I cannot call set_something() function by the const object reference?

Yes. You can only invoke const functions through a const reference.

If you need to call set_something(), then the reference will have to be held as non-const, which implies that it must be initialized from non-const, which implies that main::get_object() must return non-const, and so this decision percolates up through the entire design.

Originally Posted by brewbuck

Yes. You can only invoke const functions through a const reference.

If you need to call set_something(), then the reference will have to be held as non-const, which implies that it must be initialized from non-const, which implies that main::get_object() must return non-const, and so this decision percolates up through the entire design.

So I should just store and return non-const object in case I want to be able to call non-const functions?

Or you would go for some other design/approach?

It's hard to comment on your design when you are posting toy examples (object, set_something, etc.). Can you post a real class that you are implementing this way?