Processing 1.0 - Processing Discourse - I need to use a pointer

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Index › Programming Questions & Help › Syntax Questions › I need to use a pointer

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I need to use a pointer (Read 354 times)

bmud

I need to use a pointer
Jul 15^th, 2008, 7:38pm

Here's the problem, simplified...

I've got two boxes. I call them A and B. Both are objects of the class "Module" which has a number of sub-classes.

There's also a list menu. When something on the menu is pressed the selection of A or B is changed. Here's some Pseudo Code:

if(top is selected){
  selected = A
  switch to the bottom
}else{
  selected = B
  switch to the top
}

The trouble is this part.
Code:

selected = A

I don't usually use pointers, but for this scenario I have to. Otherwise, I have to copy everything that can happen for A and B in to two lists with different left-sides because the next part right now looks like this Code:


switch(menu_index){
  case 0: selected = new SubOne(a,c,b,d,e,f,g);
  case 1: selected = new SubTwo(h,i,j,k,l,m);
  case 2: selected = new SubOne(n,o,p,q,r,s,t);
  case 3: selected = new SubThree(u,v,w,x,y,z);

and so on... Can I please make a pointer? Help?? This sketch is already enormous. I can't afford to make two lists of all these menu commands.

JohnG

Re: I need to use a pointer
Reply #1 - Jul 15^th, 2008, 7:47pm

Java doesn't have pointers, everything is a reference.

I'm not quite sure what you're trying to do.. but I believe you can just do"selected = A"

e.g.
Code:

class foo{
  int x;
  foo(int y){
    x=y;
  }
}

foo A,B;

void setup()
{
  A=new foo(1);
  B=new foo(2);
}

void draw()
{
  foo C;
  if(thing)
    C=A;
  else
    C=B;
}

This doesn't copy A to C, it just says that C is a reference to the same object as A is.

bmud

Re: I need to use a pointer
Reply #2 - Jul 15^th, 2008, 8:10pm

Thanks for the speedy reply! It got me back on the right track. I think I understand what's happening.

I can do C=A or C=B...
but the functions of the menu can't use Code:

C = new Subfoo(d,g,e,g,d)

because C is its own object.

Instead, I think I'll have to put the two items (though there are only two) in to an array. Then, I can attack the global variable but in a different way. It's like.. make-shift memory addresses.

JohnG Ex Member	Re: I need to use a pointer Reply #3 - Jul 15^th, 2008, 9:08pm I think you can just do it in reverse... e.g. Code: thing C; switch(something) { case 1: C=foo1(...); break; case 2: C=foo2(...); break; } if(top is selected) A=C; else B=C;

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