Re: Storing data in a TreeIter (custom TreeModel)

[muppet <scott asofyet org>]

On Wednesday, May 26, 2004, at 07:32 PM, Zach Bean wrote:

> The problem is this: I'm having some trouble actually storing data in 
> a TreeIter :o)

rule of thumb: since GtkTreeIters are ephemeral and give us no 
destruction hooks, we cannot actually store data *in* Gtk2::TreeIters 
-- you can only reliably store extra references to things you have 
elsewhere.  for example, you can put in an iter a reference to an 
element of a list you keep in your model; the model's data structure 
actually owns the reference, and the iter holds only a throwaway copy 
of the reference.  you can't really make an iter own anything.  sorry.


thus...

> return [$self->{_stamp}, ($id+1)-1, \$sibling, \$parent];

if $sibling and $parent are lexicals, and not copies of data existing 
somewhere else, they will cease to exist at the end of this function, 
and the iter will contain stale pointers.


> The plus-one-minus-one thing seems to be necessary to get $id, which 
> came from the DB through DBI, into the TreeIter, which wants an 
> integer for the second field.  For some reason, XS's SvIOK wouldn't 
> return true unless I did that.  This seems to work well.

it may actually be a string, e.g., SvPOK is true.  $id+0 should work as 
well, and may be a little clearer.


--
He's so good, you're gonna rock, and if you don't rock, it's your own 
fault.
  -- kk, describing the perks of having a very good drummer.