Pointer always returning NULL

[Tyler Hummel]

Hello,

Whenever the below code goes through the pointer transition always returns NULL despite being edited in the function.

This happens 60 times a second:

      current_room->transition(transition);
      if(transition!=NULL)
      {
        current_room=transition;
        transition=NULL;
      }

Transist changes to 1 on click:

void room_intro::transition(base_room* next)
  {
    if(transist>0)
    {
      switch(transist)
      {
      case 1: next = new room_floor1_1(); break;      
      }
    }
  }

So when clicked transition should go from NULL to a new room_floor_1_1 but it always returns NULL. I can't seem to find why this is happening.
Any help would be greatly appreciated.
Thanks,

Tyler

[Peter87]

The pointer is passed by value so the pointer inside the transition function is a copy of the pointer you pass to it. Changes made to the copy (inside the function) will not affect the original pointer.

[Tyler Hummel]

I'm not sure how it's being passed by value when I set it to be passed by address here:
void room_intro::transition(base_room* next)

[Angeljruiz]

when */& is used in prototype and declarations it just means it a pointer, its not a dereference/reference operator
Sorry if that didnt make sense :p

[helios]

The pointer itself is being passed by value.

Quick fix:

void room_intro::transition(base_room*& next)
  {
    if(transist>0)
    {
      switch(transist)
      {
      case 1: next = new room_floor1_1(); break;      
      }
    }
  }

Alternatively:

current_room->transition(&transition);

//...

void room_intro::transition(base_room** next)
  {
    if(transist>0)
    {
      switch(transist)
      {
      case 1: *next = new room_floor1_1(); break;      
      }
    }
  }

[Tyler Hummel]

Huh, I honestly didn't know it worked that way. Thanks for your help everyone.

Tyler