On Mon, Mar 5, 2012 at 4:13 PM, Daniel Nouri <[email protected]> wrote:
> On Mon, Mar 5, 2012 at 9:27 PM, Jasper van den Bosch <[email protected]> wrote:
>> I have a question for the traversal users:
>>
>> do you
>>
>> a) load your model from data (i.e. sqla) and add the resource properties
>> (request, __parent__) in the parent?
>
> There's no reason your models can't just implement __parent__ and
> __name__ as properties themselves. These have nothing to do with
> HTTP. (No need to know about the request for traversal!)
>
> An example using SQLAlchemy:
> https://github.com/Pylons/Kotti/blob/master/kotti/resources.py#L108
So how would you apply this to a normal SQLAlchemy database, that may
have the concept of name and parent but not in the resource structure?
In particular, an ordinary 1:many relationship where the parent has
several children with a backref to itself, but not using the words
"name" and "parent".
class Main(Base):
id = sa.Column(sa.types.Integer, nullable=False, auto_increment=True)
subs = orm.relationship("Sub", backref="main")
class Sub(Base):
id = sa.Column(sa.types.Integer, nullable=False, auto_increment=True)
main_id = sa.Column(sa.types.Integer, sa.ForeignKey("Main.id"),
nullable=False)
In this case, the 'id' fields can serve as the .__name__, converting
them to a string if necessary. And the 'main' backref is equivalent to
.__parent__. So would the name and parent simply return these
properties? Do we need to do anything to prevent unnecessary queries
for parent?
For large tables, I generally defer the fields that are only used on
the details page and searching -- i.e., not on index pages -- in a
deferral group called 'details'. So if you fetched a Sub and referred
to its parent (probably wanting only the ID and title fields for a
hyperlink, and perhaps a date for sorting), only the fields used
'everywhere' would be loaded. I guess that would "just work" in a
Resource scenario.
Of course, when fetching a sub, there's no place in the API to specify
whether you'll be wanting all its detail fields, unless you query the
database directly, in which case you can't go through the resource
tree.
--
Mike Orr <[email protected]>
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