using arrays in custom properties

[Ben Rubinstein]

on 11/3/03 12:22 am, David Epstein wrote

> The first comments on this question puzzled me, as they involved setting
> custom property SETS, whereas the question seems only to deal with custom
> properties themselves.

I think this reflected on a confusion I had.  My understanding was that one
could think of custom properties in three steps (let's say, one could learn
about them by three observations):

 a) objects can have custom properties:
        set the abc of object x to y

 b) these custom properties can be arrays, in which case the syntax is
        set the abc[k] of object x to y

 c) custom properties can be grouped in sets, allowing one for example
    to have one set of custom properties for the English version of an
    app, another for the French version.

I didn't really care about the last of these three observations.  As far as
I was concerned, my question related to the second; I had no interest in
custom property sets, I was just interested in custom properties which
happened to be arrays.  I said:

> I'm storing an array in a custom property of an object.

Like you, my first reaction to the initial responses was that they had got
the wrong end of the stick.  But before I wrote back saying 'thanks very
much, but this isn't what I'm asking' I actually tried some of the
suggestions, and realised it worked...

So, I'm now coming to see - or at least believe in - a different model.
JEANNE OR SOMEONE PLEASE CORRECT ME IF I'M STILL IN ERROR!  What I now
believe is something like this:

 a) objects can have named arrays associated with them.  These arrays
    are known as 'custom property sets'.  They are accessed using the syntax
        set the abc[k] of object x to y

 b) one of these arrays can be set as the default, for which there is a
    special syntax, in which you don't need to specify the name of the
    array, Such that (if the 'abc' array is set as the default)
        set the k of object x to y

    is equivalent to
        set the abc["k"] of object x to y


    (note the quotes!)

 c) ...and then there are some minor details, as follows:

    - some extra syntax: the 'customKeys' property returns the keys of the
    current 'default' array.  Setting the 'customKeys' deletes or creates
    keys accordingly - newly created keys have empty values.

    - one of these arrays, initially the 'default' array, has no name.  You
    can only access this array when it is the default array, using the
    secondary syntax noted above.

    - some extra syntax: the 'customPropertySet' property is the mechanism
    for selecting which array is to be the 'default' array (where empty
    refers to the 'set with no name').

    - some extra syntax: the 'customPropertySets' is a property which
    returns the list of arrays (not counting the one with no name); and
    which allows you to effectively delete one or more of the existing
    arrays.


In other words, rather than there being two things (custom properties, and
custom property sets); or even three things (simple custom properties, array
custom properties, and custom property sets); there is only thing: custom
property sets, which are arrays.

I don't know if this model is exactly right.  It certainly seems to
correspond better with the observed behaviour, and gives me a better basis
for predicting the effect of different code, than the one I had before.

I'd be interested in comments from those more experienced in these
matters...!
 
  Ben Rubinstein               |  Email: benr_mc at cogapp.com
  Cognitive Applications Ltd   |  Phone: +44 (0)1273-821600
  http://www.cogapp.com        |  Fax  : +44 (0)1273-728866