[Zope-dev] Re: Zope and Storm (SQL)

[Philipp von Weitershausen]

Martijn Faassen wrote:
> David Pratt wrote:
> [snip]
>> For me, the crux of the rdb approach for legacy code is the container, 
>> location and traversal. You have been very generous with your 
>> examples. I am really hoping for a clearer idea of handling Container, 
>> OrderedContainer, and Location which is prevalent in legacy code. 
>> Overall, I can say that I quite the innovation here in getting to a 
>> 'leaner' concept of Zope.
> 
> I myself wouldn't be inclined to call Container and Location only 
> relevant to legacy code.
> 
> It's very convenient to have a RDB-backed object have a location, as 
> that allows you to get the URL for it in the regular manner.

Right. ILocation makes sense everywhere you want to place any sort of 
objects (whether ZODB or not) in a hierarchy. Such hierarchy can then be 
used by URL generation, security policies (for acquiring security 
settings), etc.

Also, containers make a lot of sense since they essentially are like 
tables or table views.

> For Container, in the megrok.rdb prototype code we actually make 
> containers be SQLAlchemy 'MappedCollection' objects. MappedCollection 
> happens to implement the container API already.

Note that naively speaking, the IContainer and dict APIs are the same. 
But technically, they're not entirely. dict keys can be anything 
hashable. IContainer keys must be unicode or str objects.

> This way we can make relations be containers by writing something like:
> 
> class Departments(rdb.Container):
>     # this is a MappedCollection
>     rdb.key('title')

I think here it would be great if the grokker for rdb.Container could 
somehow find out whether 'title' was a text column. If it's not, it's 
not a valid container key, unless perhaps rdb.Container contained some 
conversion magic.

> class Faculty(rdb.Model):
>     # rdb.table_name('faculty') is the default
>     __tablename__ = 'faculty'
> 
>     grok.traversable('departments')
> 
>     departments = relation('Department',
>                            backref='faculty',
>                            collection_class=Departments)
> 
> 
> The 'departments' attribute is a container you can traverse into this 
> way. You can hook up views to Departments just like you would to any 
> container.

Yep. Very nice :)