Charlie Groves wrote:
> Hi,
>
> I've got a setup like this
>
> categories = Table("categories", engine,
> Column('transaction_id', Integer,
> ForeignKey('transactions.id'),
> primary_key=True),
> Column('name', String, primary_key=True))
> class Category(object):
> pass
> assign_mapper(Category, categories)
> transactions = Table("transactions", engine,
> Column('id', Integer, primary_key=True),
> Column('recipient', String),
> Column('amount', Numeric),
> Column('datetime', DateTime))
> class Transaction(object):
> pass
> assign_mapper(Transaction, transactions,
> properties={'categories':relation(Category.mapper)})
>
> With that, Transaction objects have a categories list and I can append
> Category objects to it and get Category objects back out and I'm
> moderately happy. I'd be really happy if I could get the categories
> list to be a list of strings that represent the name column from
> category so I could do
>
> t = Transaction()
> t.categories.append('food')#creates a Category with name food and
> links it to t.id
> objectstore.commit()
>
> and then at some later date do
>
> if 'food' in t.categories:
> #do something depending on the transaction relating to food
>
> and so on. Essentially, I don't like explicitly dealing with a
> Category object when I really just care about one field inside of it.
>
> Is this possible using the mappers or something like that?
>
> Am I trying to do something ridiculous? I'm new to this whole ORM game.
>
> Thanks,
> Charlie
>
>
The easy way is to add a couple of methods to your Transaction class:
class Transaction(object):
def getCatNames(self):
return [x.name for x in self.categories]
def addCatName(self, name):
newcat = Category.mapper.get(name)
if newcat is None:
newcat = Category()
newcat.name = name
self.categories.append(name)
# it's also easy to make the 'get' part a property:
catnames = property(getCatNames)
... but making the 'set' part act like a property is more challenging.
My bet is that as soon as you do all that work, you will discover that
you need to add a column to your properties table.
-- Wade Leftwich
Ithaca, NY
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