Protected value changed between setting and use

[jakesalomon]

Hi Y'all.

Another beginner question, although I'm getting into the esoterics here. As I mentioned in my post last week, I am going through Bucky Roberts's 9+ hour video and have gotten up to the section on polymorphism. (Yes, I will look into learnc.com later.) Not yet done with the lesson (so I haven't gotten up to the real meat) but I'm having trouble with the intermediate setup.

Following Bucky's example closely (but not aping everything) I created a base class named Enemy with a protected variable attackPower and public method setAttackPower(). I then created two derived classes named Nonja and Monster. Each has a method called attack().

I created a variable each derived class and called setAttackPower for each of these variables, with a different value to set for its instance of variable attackPower. Here's the code; results after the code section.

#include <iostream>

using namespace std;


class Enemy
{
 protected:
  int attackPower;

 public:
  void setAttackPower(int a)
  {
    int attackPower = a;
    cout << "Enemy::attackPower has been set to " << attackPower << endl;
  }
  void showAttackPower()
  {
    cout << "Current value of attackPower = " << attackPower << endl;
  }
};

class Ninja: public Enemy
{
 public:
  void attack()
  {
    cout << "I am Ninja. Must attack you at level: " << attackPower << endl;
  };
};

class Monster: public Enemy
{
 public:
  void attack()
  {
    cout << "I am Monster. Must eat you at level: " << attackPower << endl;
  };
};

int main()
{
  Ninja nin;
  Monster mon;

  nin.setAttackPower(29);
  mon.setAttackPower(99);

  nin.attack();
  mon.attack();

  return 0;

}

When I run in codeblocks I get this output:

Enemy::attackPower has been set to 29
Enemy::attackPower has been set to 99
I am Ninja. Must attack you at level: 4354206
I am Monster. Must eat you at level: 2686868

YIKES! What happened? Where did those crazy values come from?

On the other hand, when I run the same code under the C++ compiler in my CygWin64 environment, I get this:

Enemy::attackPower has been set to 29
Enemy::attackPower has been set to 99
I am Ninja. Must attack you at level: 0
I am Monster. Must eat you at level: 0

Funny, I did the same thing again and got a different result. Time for sanity self-check? ;-)

Either way, it ain't what I set it to. What am I doing wrong?

(BTW, I'm not getting the preview or tags by clicking the icons. My apologies for any bad formatting.)

Thanks for help here.

-- Jake S. (Pronounce that out loud and you'll know how I'm feeling. :-)

[zapshe]

You made a slight epic fail.

You put "int" in front of "attackPower", so you're actually just changing a new local variable.

void setAttackPower(int a)
  {
    int attackPower = a; //This is a NEW VARIABLE
    cout << "Enemy::attackPower has been set to " << attackPower << endl;
  }

So when you output the actual variable, you're getting junk since the variables were never initialized.

[jakesalomon]

THANK YOU zapshe! That was exactly it!

If you meet me on the street, do not ask why I have a bruised, flattened forehead!

Now, how do I mark this thread closed/solved?