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Quick Question about Pointers

Started by 1kevgriff Nov 17, 2000 at 9:16 PM 5 replies 550+ views

Original Post

Nov 17, 2000 at 9:16 PM

At first, when I learned about pointers, I said to myself "When am I ever going to use these?" Well, now that I''ve been programming for a while, I think I know why pointers would be useful - but I don''t want to mess with the code I have written so far (at least 10 hours of work). So, I''ll ask a question here to see if what I''m thinking is right. Let''s say I create a object in one function that is used just to set up character profiles (for a game). Well, after that function is done running - the object is lost. Can I use a pointer (or *gulp* a series of pointers) to keep all of the class information on the freestore? Then when the program exits, have another function remove them from the freestore? Just curious. Thanks

djsteffey

165

djsteffey

Nov 17, 2000 at 9:20 PM

is this what you mean

  

void main()
{
  Object* myObject;
  allocateMem(myObect);
// now i can do anything with myObject

  myObject.doStuff();
  deallocateMem();
}

void allocateMem(Object* myObject)
{
  myObject = new Object;
}

void deallocateMem(Object* myObject)
{
  delete myObject;
  myObject = null;
}

if that is what you mean, then you can do that and it should be fine

"Now go away or I shall taunt you a second time"
- Monty Python and the Holy Grail
themGames Productions

Succinct

Nov 18, 2000 at 9:18 AM

here''s what i''m seeing happen

tProfile* CreateNewProfile( )
{
    tProfile NewProfile;

    return &NewProfile
}

that won''t work, cuz NewProfile is allocated on CreateNewProfile()''s stack, not the freestore, and so is destroyed when the function returns.

if i''m right, here''s what u''d need to do:

tProfile* CreateNewProfile( )
{
    tProfile* NewProfile = new tProfile;

    return NewProfile;
}

void KillProfile( tProfile* pProfile )
{
    delete pProfile;
}

hope this was what you meant

//////////////////////////////

I have no name that you may call me. I am Succinct, so call me as such.

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1kevgriff

Author

1kevgriff

Nov 18, 2000 at 10:51 AM

Thanks for the responce. Got the exact answer I needed.

1kevgriff

Author

1kevgriff

Nov 21, 2000 at 2:31 PM

Maybe I spoke too soon on the last post. Here is what i write:

    

Mp3* Fade;   // create object "Fade" with class "Mp3"

Fade = new Mp3;    // put Fade on the freestore


// ... later in code


Mp3.Load("c:\\mp3\\fade.mp3");  // Run a function of Mp3

                                // Error recieved!

Why can't I use the class functions?

Edited by - Coaster Kev on November 21, 2000 3:32:16 PM

Claus Hansen Ries

Nov 21, 2000 at 2:41 PM

There exsists no Mp3 but a pointer to a Mp3 object.

Fade->Load("c:\\mp3\\fade.mp3");

karmalaa

Nov 26, 2000 at 3:48 PM

quote:
Original post by ncsu121978

is this what you mean [...]

if that is what you mean, then you can do that and it should be fine

I don''t think it would work. It should be

    

void main()
{
    Object *myObject;
    allocateMem(&myObject);
    myObject->doStuff();
    deallocateMem(&myObject);
}

void allocateMem(Object **myObject)
{
    *myObject = new Object;
}

void deallocateMem(Object **myObject)
{
    delete *myObject;
    *myObject = null;
}

You have to use TWO LEVELS of indirection. Or just use C++ references...

Bye,

Karmalaa

---
"Lifting shadows off a dream once broken
She can turn a drop of water into an ocean"

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