simple question on Class-Members

Hi, I have a question:

Code:

---

class DOOR {
           public:
           ........
           draw();
}

---

Code:

---

class build {
          public:
          ........
          std::vector<DOOR> door;
          QImage imm;
};

---

I need to use variable imm within member draw(). How can I do?
Thanks

What calls that DOOR::draw() method? Maybe you invoke it only from build class?

Code:

---

void DOOR::draw() {
   imm="hello\n";
}

---

I'd like use imm in ::draw () and I'd like can use "only" imm and not other variables of Build class.....

Quote:

---

Originally Posted by mickey

I'd like use imm in ::draw () and I'd like can use "only" imm and not other variables of Build class.....

---

But where do you intend to use thet DOOR::draw() method?

now I don't know.
I'd like use imm within Door:draw() and compile it.
Thanks.

Quote:

---

Originally Posted by mickey

now I don't know.

---

So maybe you should redesign your classes?

For example like this:

Code:

---

void DOOR::draw( const QImage& img ) 
{
   // ...
}
 
void build::draw()
{
   // ...
   for( std::vector<DOOR>::iterator it = door.begin(); it != door.end(); ++it ) {
      it->draw( imm );
   }
   // ...
}

---

Other possibility is that each of DOOR instances would hold a pointer or reference to a build instance:

Code:

---

void DOOR::draw() 
{
   // ...
   QImage img( _build->image() );
   // ...
}
 
const QImage& build::image() const 
{
   return _imm;
}

---

Everything depends on the way you want to use those two classes and on things what they represent.

OK thanks. But why do you use underscore symbol?

Quote:

---

Originally Posted by mickey

why do you use underscore symbol?

---

In this case is just a habit.

In my code I add underscore to member variables to distinguish them from parameters.