On Sep 23, 2013, at 11:52 AM, Michael Bayer <mike...@zzzcomputing.com> wrote:
> > On Sep 23, 2013, at 11:15 AM, Donald Stufft <donald.stu...@gmail.com> wrote: > >> >> >> Well mostly I've isolated other pieces of global state and while metadata >> itself probably isn't a problem I was hesitant to add it as a piece of >> global state since I didn't have anything else like that. I did come up with >> a solution though that I think works Ok. It's basically allowing me to >> declare my tables at the top level (but not use them from there) so that I >> can organize my code better, but then the "real" tables exist inside of my >> application object where I can use them. >> >> Examples here: >> >> https://github.com/dstufft/warehouse/blob/werkzeug/warehouse/packaging/models.py >> https://github.com/dstufft/warehouse/blob/werkzeug/warehouse/models.py >> https://github.com/dstufft/warehouse/blob/werkzeug/warehouse/application.py#L37-L46 >> >> I haven't settled on this approach (notably I need to figure out how it's >> going to interact with alembic) but so far It seems to work alright. > > > In this pattern, warehouse.packaging.models has a dependency on "from > warehouse import models" in order to get at the Table stub class - then the > application module reaches down into a set of warehouse.* modules to get at > the tables it wants. warehouse.packaging.models is reluctant here to > declare itself as a part of something - it would rather that external actors > reach down to get at it. > > If the warehouse.Table class were an actual SQLA Table object, and the > original question, "can I attach .metadata after the fact" were being used > here, this pattern would be a little broken - because > warehouse.packaging.models is advertising itself as "please reach down and > use me!", but then, "oh only *one* of you can use me!" - basically, > warehouse.application would be *setting global state* into a module that has > gone through great lengths to avoid knowing about any global state. I find > declaration of state ownership preferable to runtime injection of that > ownership. > > if you just changed line 17 of warehouse.packaging.models from "from > warehouse import models" to "from warehouse.models import metadata" and then > used sqlalchemy.Table directly, you'd trim out a lot of quasi-reinvention > here and make things a lot more idiomatic to outsiders IMHO. Yea I eventually removed most of that. The database is pretty much a global either way. (Being a shared external resource) so trying to pretend it isn't wasn't being very helpful. I ended up doing: https://github.com/dstufft/warehouse/blob/werkzeug/warehouse/application.py#L38-L42 https://github.com/dstufft/warehouse/blob/werkzeug/warehouse/application.py#L50-L52 https://github.com/dstufft/warehouse/blob/werkzeug/warehouse/packaging/models.py Which I think is pretty much the same as what you suggested. ----------------- Donald Stufft PGP: 0x6E3CBCE93372DCFA // 7C6B 7C5D 5E2B 6356 A926 F04F 6E3C BCE9 3372 DCFA
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