[Zope3-Users] Multi-level object structure

[Markus Kemmerling]

Am 08.08.2008 um 17:24 schrieb Jeronimo Jacobo:

> Hi
> I am new in Zope 3 world, i have read the book " Web Component  
> Development with Zope 3" and I am designing a Zope application  
> which involves a multiple-level object structure in which the  
> father class has multiple instances of son class and the son class  
> has multiple objects of the grandson class.
> Up to now i have managed to construct something like this:
>
> class IGrandson(Interface):
>    age=Int(
>       title=_(u'Age'),
>       description=_(u'The age of the Grandson'),
>       required=True
>     )
>    name=TextLine(
>         title=_(u'Name'),
>         description=_(u"The name of the Grandson"),
>         required=True
>         )
>
> class ISon(Interface):
>     name=TextLine(
>         title=_(u'Name'),
>         description=_(u'Name of the Son'),
>         required=True,
>         )
>     grandsons=List(
>         title=_('Grandsons'),
>         description=_("A list of Grandsons"),
>         required=False,
>         value_type=Object(
>             title=_('Grandson'),
>             schema=IGrandson
>             )
>         )
>
> However, in this way i can only create Sons. Grandsons will be  
> added as an element of the Son''s grandsons list. If I want to  
> create a Grandson without father, how can I add it later to the  
> Son''s list?
>
> Is the List the most effective way to store objects? I have tried  
> with BTrees, but then i have problems to construct the widgets and  
> views to add elements to the BTree and i think BTrees is not an  
> interfaces so I cannot do something like:
>
> grandsons=OOBTree(
>         title=_('Grandsons'),
>         description=_("A list of Grandsons"),
>         required=False,
>         value_type=Object(
>             title=_('Grandson'),
>             schema=IGrandson
>             )
>         )
>
> nor
>
> grandsons=Object(
>             title=_('Grandson'),
>             schema=OOBTree
>
>         )
>
> Also, considering that the structure can grow up to four  
> generations (granpa, father, son, grandson), what will be the best  
> approach to achieve this mult-level structure?
>
> My initial idea was to present in the first view the Granpas. When  
> selecting one of them, its attributes will be shown, among them its  
> sons (the Fathers). Then when selecting one of them, the process  
> will repeat until the grandson.
>
> I appretiate much your help and ideas. Thanks in advance.
>
> Jeronimo

You could implement everybody as a container for objects of the same  
type as the container itself, something like this:

IGenealogy(IContainer):
     ...

IPerson(IContained, IContainer):
     contains('. IPerson')
     containers('. IPerson', IGenealogy)

    age=Int(
       title=_(u'Age'),
       description=_(u'The age of the Person'),
       required=True
     )

    name=TextLine(
         title=_(u'Name'),
         description=_(u"The name of the Person"),
         required=True
         )

This way the father-son relation will only be a matter of the parent- 
child relation and not a feature of the defining interface itself  
(some day every son may become a father himself ;-).

Regards,
Markus Kemmerling