Question about protected variables 1

[hylian90]

Hey y'all. I have a question about protected variables within a class. Let's say you have a base capability class called BASE, and two derived classes, DERIVED1 and DERIVED2. Each of these derived classes has three protected variables. My question is this: Can DERIVED1 access DERIVED2's protected variables? To put it technically, can classes derived from the same base access each others' protected variables? Thanks! :

Brian



I have no idea what MIS means

 

[xwb]

Answer to your question: No

MIS=Management Information Systems
No idea what that means but it has nothing to do with management

 

[globos]

Actually, yes it is possible. The mechanism is called class friendship. Have a look at the `friend' C++ keyword.
Here is a small example to illustrate how it works :

#include <iostream>

class Derived2;//forward declaration

class Derived1
{
  //routines of Derived2 can access private features of Derived1 :
  friend class Derived2;
protected:
  int _j;
};

class Derived2
{
public:
  // A dummy access to Derived1::_j.
  void please_do_it (Derived1& d1)
  {
    std::cout << "d1._j = " << d1._j << std::endl;
  }

protected:
  int _i;
};


//Little test.
int main ()
{
  Derived1 d1;
  Derived2 d2;

  d2.please_do_it (d1);
  return 0;
};

--
Globos

 

[hylian90]

Actually, that's rather ironic, considering the two classes are called "player" and "enemy." You would think they'd be anything but friendly.
Enemy --><-- Player

--------------------------------------

//Program to tick off my sister

Programming is officialy a life skill

I have no idea what MIS means

 

[ArkM]

1. It's not the best style: all capitals in class names; traditioanally it's reserved for macros names...
2. Derived1 is NOT a kind of Derived2. It's not the best design (it's the worst design: to access D1 protected members from D2 (and vice versa).
3. About last note above: yes, it's funny, but it's a good design tip - don't do that (enemy as a friend of player and vice versa...

 

[hylian90]

About the caps, I just did that so it would be easier to see the actual class names from the type.

As for two . . . I'm working on that. But I need members of enemy to be able to access members of player so that they can reassign their HP variable.

Three . . . Just making an observation

--------------------------------------

//Program to tick off my sister

Programming is officialy a life skill

I have no idea what MIS means

 

[jstreich]

Suggestion would be to make mutator functions in the base class that both classes then inherit.