[Bf-python] FW: [Bf-blender-cvs] CVS commit:blender/source/blender/python/api2_2xObject.c

[Gilbert, Joseph]

I'm doing a similar thing for Armature api. I have a typeobject that
functions like a dictionary for dealing with bones. 
I think you can also subclass from list/dict if you want all the
functionality++. There is an article here:
http://python.fyxm.net/peps/pep-0253.html. You just override the tp_base
member. 
In my case I couldn't subcalass because I wanted to have insertion
checking.
Maybe a good idea is to add some TypeObjects to the API that are generic
objects that do insertion type checking, etc. You could embed these in
objects that require list or dictionary access but needs some stricter
controls over what can go in or out. This class could be subclasses if
needed. 

-----Original Message-----
From: bf-python-bounces at projects.blender.org
[mailto:bf-python-bounces at projects.blender.org] On Behalf Of Stephen
Swaney
Sent: Sunday, November 06, 2005 1:19 PM
To: Blender Foundation Python list
Subject: Re: [Bf-python] FW: [Bf-blender-cvs] CVS
commit:blender/source/blender/python/api2_2xObject.c

On Thu, Nov 03, 2005 at 07:39:05AM -0800, Ken Hughes wrote:

> It's not just here, it's in a number of places.  For example, NMesh, 
> Mesh and Object deal with a list of materials instead of a sequence 
> operator; the individual Material objects are wrapped but the list 
> isn't.  So to assign new materials, you have to assign the whole list,

> not just a single material:
> 
>    matlist = obj.materials
>    obj.materials = [matlist[0],matlist[1],mat2]
> 
> instead of
>    obj.materials[2]=mat2
> 
> The problem is we would also need to implement a bunch of new sequence

> operators for these types, and there may not be any guarantee that the

> way Blender internally represents one type is the same as another
(could 
> use array in one case, linked list in another).

I've been thinking about this since we started the tp_getset stuff.
A lot of our bpy types - which are slowly becoming classes - have
a list as a member attribute.  Ideally, we would like to script
something
like 
  obj.materials[2]=mat2

So far, the best solution I have is to create little helper classes
like a MaterialList with their own sequence operators.  These helper
classes would enforce their own constraints like list length or 
element type.

As for Blender's internal representation, from an interface point of
view, I don't think we need to be limited by whether the underlying
data is an array or linked list, for example.  Think of the Bpy API is
like a giant Adaptor Class in the Design Patterns sense.  Our goal is to
present a consistent, orthogonal interface for the user no matter what 
the underlying data looks like.

-- 
Stephen Swaney
sswaney at centurytel.net

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