On Thu, Dec 10, 2015 at 12:31:33PM -0500, Mike Bayer wrote: > > > On 12/10/2015 10:21 AM, Michal Petrucha wrote: > > Hello alchemists, > > > > There's something that's been bugging me for a while now. I even > > asked about it on [stackoverflow][1], but it didn't get much > > attention there. It's been suggested to me on IRC that this > > mailing list might be a better place for this question. > > > > When you take a look at the [table_per_relation ORM example][2], > > you can see that the argument passed to `ForeignKey` [here][3] is > > the “raw” “tablename.column”. However, since the entire point of > > declarative is to use higher-level constructs to abstract away > > some of the lower-level SQL details, it would make sense to me to > > use `cls.id` here instead. (I want this here declarative field to > > point to this other declarative field, instead of saying, I want > > this declarative field to point to this SQL column of that SQL > > table.) > > the first thing I don't understand is that the code you refer to is > locating the correct name dynamically. So why does it matter? You > aren't typing in the name of the table or class yourself.
Why does it matter? Let's say it's a matter of personal taste and
consistency -- I like to use the ForeignKey(OtherClass.id) API rather
than ForeignKey('other_table.id'), and I like to be consistent about
which APIs I use.
Not to mention that in this particular example, typing
ForeignKey(cls.id) would be a lot shorter and require less brainpower
to parse than ForeignKey("%s.id" % cls.__tablename__).
> Second thing is, you can pass the class-bound column to the
> ForeignKey, sure, just as an object, not a string:
>
> ForeignKey(WhateverClass.id)
>
> it just requires that you have WhateverClass already available.
Exactly -- and the point of my question was that this apparently
doesn't work in that example; I assume it is because the class is not
fully initialized at that point, and I'm wondering if there's anything
that can be done about it.
Cheers,
Michal
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