Thanks for all of the replies This is a very responsive group!
I'm still not clear on how to replicate some of the Django
functionality here but at least I think I understand how many-to-many
works in web2py.
I had seen the tagging example before but something about that method
bothers me. It reminds of a Clarion DOS app we use at work from 25+
years ago. There was a many-to-many relationship between models &
options. The solution was to store a list of option ids in a field in
the model table. The idea was almost identical except instead of |1|2|
3|4| it was just a regular comma separated list 1,2,3,4.
Another question about the example I am trying to convert:
In the django app, the 'last' field in the Event model is used such
that only one 'event' per user can have latest=True. They accomplish
this by using django's manager class, a custom filter and overriding
the save method of the model.
So in the model file
def today():
now = datetime.now()
start = datetime.min.replace(year=now.year, month=now.month,
day=now.day)
end = (start + timedelta(days=1)) - timedelta.resolution
return (start, end)
class EventQuerySet(QuerySet):
def today(self):
return self.filter(creation_date__range=today())
class EventManager(models.Manager):
def get_query_set(self):
return EventQuerySet(self.model)
def today(self):
self.get_query_set().today()
class Event(models.Model):
#....
objects = EventManager()
def save(self, **kwargs):
Event.objects.filter(latest=True,
creator=self.creator).today().update(latest=False)
super(Event, self).save(**kwargs)
So before it saves any new event, it sets any other events of that
user for today() as latest=false. I am sure there is an easier way to
do that but that is what it is in the example.
What would be the web2py way of doing something like this?
A working example of this tutorial site is still up at:
http://startthedark.com.
A link to the complete source:
http://github.com/ericflo/startthedark/tree/master
Thanks again to all for answering my previous question.
On Jul 28, 6:41 pm, Yarko Tymciurak <yark...@gmail.com> wrote:
> You should be aware that this "tagging" style is ok, and works - but the way
> it works may not be the right thing for your application.
>
> If you have limited references (say ~20 or so per a "many") then this is
> simple, efficient, and you can probably manage your many-to-many this way.
>
> What this does is stores a set of table references (integers, basically) as
> text delimited by "|", so you would have a reference in this style which
> looks (for example) like
>
> "|1|27|153|225|"
>
> and your code would need to parse it.
>
> To have "many" to "many", you would just have cross references like this,
> one of the tag-style "many" definitions in each of two tables.
>
> I like the traditional way to do this, and that is to define a table to hold
> the many, and there are advantages depending on what you want to do.
>
> For example:
>
> db.define_table('location',
> Field('name'))
> db.define_table('transportation',
> Field('name'))
>
> # many-to-many table - holds what transportation is available where
> db.define_table('available',
> Field('location', db.location),
> Field('transport', db.transportation))
>
> Now you can define sets for operations like this:
>
> transport_list = ((db.location.id == db.available.location)
> & (db.transportation.id == db.available.transport))
> for row in transport_list.select():
> print row.location.name, row.transport.name
>
> On Tue, Jul 28, 2009 at 2:42 PM, Fran <francisb...@googlemail.com> wrote:
>
> > On Jul 28, 5:47 pm, __future__ <wrigh...@gmail.com> wrote:
> > > I am already confused about how to implement the Django style many-to-
> > > many relationship in web2py.
>
> > The Many<>Many support native to Web2Py is the Tagging-style:
> >http://www.vimeo.com/2720410
>
> > F
>
>
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