On Jun 4, 10:58 am, Doug Warren <doug.war...@gmail.com> wrote:
> I don't believe I want to local_import my db.py file as it's already
> set up by the environment correct?
Correct - you do not want / need to import your db.py.
As long as it is in your models folder (by default it is), it's
already in your request context before your controller is called.
>
> What I'm asking for is a way to keep all of the code that relates to
> the model in one place and to invoke it from controllers. That is if
> I define 5 tables for the model I'd expect to write helper functions
> to manipulate all 5 tables and not to have the controller know the
> intimate details of the model. That's the concept behind Object
> Orientated programming isn't it? Objects are black boxes to other
> objects other than their public facing interface.
Right - but DAL is just a Data abstraction layer (i.e. an SQL adapter,
if you will), not an ORM (i.e. there's not the level of object-
oriented abstraction that you would expect w/ an orm - it's lower
level)
So in web2py, with DAL you have knowledge of your table layout
(without direct knowledge / need for the specific back ends SQL).
You'll also find that forms, and validators are coupled to table
structure, so if / as you try to abstract away from table definitions,
you will run into this.
I'm sure others will add more comments...
>
> On Fri, Jun 4, 2010 at 8:56 AM, Yarko Tymciurak
>
> <resultsinsoftw...@gmail.com> wrote:
>
> > On Jun 4, 10:43 am, Doug Warren <doug.war...@gmail.com> wrote:
> >> Traditionally when I've written MVC style applications, the model
> >> would contain not only the data representing the objects but also the
> >> data for manipulating the objects. I'm not sure how that same
> >> relation applies to web2py.
>
> >> If I have a model that defines 4-5 tables, 2 of them are just foreign
> >> key lookups, and creating a new object involves inserting data into 3
> >> of the tables, it seems that I would want a create_object method in my
> >> model file.
>
> >> So I write something like:
>
> >> def create_object(owner_id=None, template=None):
> >> # Some sanity checking on the above
> >> new_object = db.objects.insert(template_id=template.id,
> >> person_id=owner_id)
>
> >> widgets = db.template_widget(db.template_widget.thingy_template_id
> >> == template.id).select()
> >> for widget in widgets: db.thingy_widget.insert(widget_id =
> >> widget.id, thingy_id = new_object)
>
> >> whatchymacallits =
> >> db.template_whatchymacallit(db.template_whatchymacallit.thingy_template_id
> >> == template.id).select()
> >> for whatchymacallit in whatchymacallits:
> >> db.thingy_whatchymacallit.insert(whatchymacallit_id =
> >> whatchymacallit.id, thingy_id = new_object)
>
> >> return new_object
>
> >> and place that into my db.py. Now the controller has a function like:
> >> def create():
> >> form = SQLFORM.factory( Field('template',
> >> requires=IS_IN_SET(__get_templates())))
> >> if form.accepts(request.vars, session):
> >> foo = db.create_object(owner_id=auth.auth_id,
> >> template_name=form.vars.template)
> >> response.flash = "Created"
> >> elif form.errors:
> >> response.flash = "Error (hacker)"
>
> >> Well db is referring to the DAL db not the db.py, from db import
> >> create_object gives a name not found error, so I'm at a loss as to how
> >> to define functions that work upon the model and can be invoked from
> >> one or more controllers.
>
> > I'm not sure what exactly you are saying here - but to import, use
> > local_import()
> > (seehttp://www.web2py.com/book/default/section/4/18?search=local_import)
>
> > BUT before you do, here is some background:
>
> > When a request comes into web2py, here's what happens (roughly):
>
> > web2py parses the request url, and sets up an environment to call the
> > appropriate application / controller / function;
> > Part of that setup involves running all the files in your app's model
> > folder (so that db connections, table definitions, etc. are all "there
> > for you");
>
> > This means you can put your files in the models folder, and they will
> > be run (defined) before the call to your controller.
>
> > Then, your controller / function is called.
>
> > local_import will pull in definitions / modules from your
> > application's modules folder, but you can (for development certainly)
> > just put your file in your models folder.
> > When you really want to reduce what gets run at _each_ request, you
> > might want to look at what to move to modules, so that you're only
> > pulling in those files when needed.
>
> > As for db - DAL: db is the "global" and "default" name for the db
> > connection string (it is so named and setup in the default models/
> > db.py file). You can change the name of this variable as you like
> > (or change your imports).
>
> > Hope this at least helps point you out of the forrest.
>
> > Regards,
> > - Yarko
> >> Are there any non-trivial example
> >> applications for web2py? Most of the ones that I have seen assumes
> >> that all data you need in the database can be supplied from a form and
> >> that's not the case I run into over and over again.
