Re: noob syntax question

[Sector7B]

very nice, thank you.  I will look up the book.

On Jun 24, 2:37 pm, Daniel Roseman  wrote:
> On Jun 24, 7:01 pm, Sector7B  wrote:
>
> > Thanks for the feedback and the link, all good stuff!
> > I looked at what i had written, and I think a better way to ask the
> > question is:
> > What are the mechanics behind providing "choice_set.all()"?
> > For example i have a field "choice" so having "_set" (concatenated) is
> > that generated when i run syncdb somewhere, or is that dynamically
> > interpreted at runtime?
> > My background leads me to think there would be a choice.set().all(),
> > the "_set" seems weird (to me) unless its generated.
>
> > Thanks again,
> > -j
>
> It's dynamically generated when the model class is defined. Fields can
> define a 'contribute_to_class' method, which is responsible for
> defining dynamic properties/methods on the model class. When the field
> is instantiated - which happens when the class is defined, ie when its
> module is first imported - the field's contribute_to_class method is
> executed and the related manager is created. You can see the code for
> this in django.db.models.fields.related.RelatedField. (Actually you'll
> see that contribute_to_class calls do_related_class, which calls
> contribute_to_related_class, which sets up the descriptor on the
> related model.)
>
> A very good guide to all this is Marty Alchin's book Pro Django, which
> goes into depth as to how the model metaclasses work.
> --
> DR.

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Re: noob syntax question

[Daniel Roseman]

On Jun 24, 7:01 pm, Sector7B  wrote:
> Thanks for the feedback and the link, all good stuff!
> I looked at what i had written, and I think a better way to ask the
> question is:
> What are the mechanics behind providing "choice_set.all()"?
> For example i have a field "choice" so having "_set" (concatenated) is
> that generated when i run syncdb somewhere, or is that dynamically
> interpreted at runtime?
> My background leads me to think there would be a choice.set().all(),
> the "_set" seems weird (to me) unless its generated.
>
> Thanks again,
> -j
>

It's dynamically generated when the model class is defined. Fields can
define a 'contribute_to_class' method, which is responsible for
defining dynamic properties/methods on the model class. When the field
is instantiated - which happens when the class is defined, ie when its
module is first imported - the field's contribute_to_class method is
executed and the related manager is created. You can see the code for
this in django.db.models.fields.related.RelatedField. (Actually you'll
see that contribute_to_class calls do_related_class, which calls
contribute_to_related_class, which sets up the descriptor on the
related model.)

A very good guide to all this is Marty Alchin's book Pro Django, which
goes into depth as to how the model metaclasses work.
--
DR.

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Re: noob syntax question

[Sector7B]

Thanks for the feedback and the link, all good stuff!
I looked at what i had written, and I think a better way to ask the
question is:
What are the mechanics behind providing "choice_set.all()"?
For example i have a field "choice" so having "_set" (concatenated) is
that generated when i run syncdb somewhere, or is that dynamically
interpreted at runtime?
My background leads me to think there would be a choice.set().all(),
the "_set" seems weird (to me) unless its generated.

Thanks again,
-j

On Jun 24, 3:09 am, "euan.godd...@googlemail.com"
 wrote:
> I'd add to Michael's comment that if you're unhappy with this syntax
> (I personally find it a bit odd in some cases), you can customize
> exactly what word is used there in your model definition.
>
> If you alter the choice model and add the "related_name" keyword to
> the foreign key definition, e.g.:
>
> class Choice(models.Model):
>     ...
>     poll = models.ForeignKey(Poll, related_name="choices")
>
> you can then do:
>
> >>> p.choices.create(...)
>
> On 23 June, 23:17, Michael Schade  wrote:
>
>
>
> > (Sorry in advance for the brevity and any typos, I am typing this from
> > my aging Windows Mobile).
>
> > It's quite Django-specific actually. If you take a look 
> > athttp://docs.djangoproject.com/en/dev/topics/db/queries/ it says,
> > "Django also creates API accessors for the "other" side of the
> > relationship -- the link from the related model to the model that
> > defines the relationship. For example, a Blog object b has access to a
> > list of all related Entry objects via the entry_set attribute:
> > b.entry_set.all()."
>
> > Hope that clears things up.
>
> > Michael Schade
> > Spearhead Development LLC
>
> > On 6/23/10, Sector7B  wrote:
>
> > > Hi,
> > > In the tutorial 1.
>
> > > It has this:
> > > # Give the Poll a couple of Choices. The create call constructs a new
> > > # choice object, does the INSERT statement, adds the choice to the set
> > > # of available choices and returns the new Choice object. Django
> > > creates
> > > # a set to hold the "other side" of a ForeignKey relation
> > > # (e.g. a poll's choices) which can be accessed via the API.
>
> > > and gives these examples:
> > > # Create three choices.
> >  p.choice_set.create(choice='Not much', votes=0)
> > > 
> >  p.choice_set.create(choice='The sky', votes=0)
> > > 
> >  c = p.choice_set.create(choice='Just hacking again', votes=0)
>
> > > I understand what its doing, but I don't understand where the "_set"
> > > comes from or where its resolved to.
> > > Its probably more of a python thing than a django thing, but if
> > > someone could provide insight, it would be much appreciate.
>
> > > Thanks,
> > > -j
>
> > > --
> > > You received this message because you are subscribed to the Google Groups
> > > "Django users" group.
> > > To post to this group, send email to django-us...@googlegroups.com.
> > > To unsubscribe from this group, send email to
> > > django-users+unsubscr...@googlegroups.com.
> > > For more options, visit this group at
> > >http://groups.google.com/group/django-users?hl=en.
>
> > --
> > Sincerely,
> > Michael Schadewww.mschade.me-815.514.1410

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Re: noob syntax question

[euan.godd...@googlemail.com]

I'd add to Michael's comment that if you're unhappy with this syntax
(I personally find it a bit odd in some cases), you can customize
exactly what word is used there in your model definition.

If you alter the choice model and add the "related_name" keyword to
the foreign key definition, e.g.:

class Choice(models.Model):
...
poll = models.ForeignKey(Poll, related_name="choices")

you can then do:

>>> p.choices.create(...)

On 23 June, 23:17, Michael Schade  wrote:
> (Sorry in advance for the brevity and any typos, I am typing this from
> my aging Windows Mobile).
>
> It's quite Django-specific actually. If you take a look 
> athttp://docs.djangoproject.com/en/dev/topics/db/queries/ it says,
> "Django also creates API accessors for the "other" side of the
> relationship -- the link from the related model to the model that
> defines the relationship. For example, a Blog object b has access to a
> list of all related Entry objects via the entry_set attribute:
> b.entry_set.all()."
>
> Hope that clears things up.
>
> Michael Schade
> Spearhead Development LLC
>
> On 6/23/10, Sector7B  wrote:
>
>
>
>
>
> > Hi,
> > In the tutorial 1.
>
> > It has this:
> > # Give the Poll a couple of Choices. The create call constructs a new
> > # choice object, does the INSERT statement, adds the choice to the set
> > # of available choices and returns the new Choice object. Django
> > creates
> > # a set to hold the "other side" of a ForeignKey relation
> > # (e.g. a poll's choices) which can be accessed via the API.
>
> > and gives these examples:
> > # Create three choices.
>  p.choice_set.create(choice='Not much', votes=0)
> > 
>  p.choice_set.create(choice='The sky', votes=0)
> > 
>  c = p.choice_set.create(choice='Just hacking again', votes=0)
>
> > I understand what its doing, but I don't understand where the "_set"
> > comes from or where its resolved to.
> > Its probably more of a python thing than a django thing, but if
> > someone could provide insight, it would be much appreciate.
>
> > Thanks,
> > -j
>
> > --
> > You received this message because you are subscribed to the Google Groups
> > "Django users" group.
> > To post to this group, send email to django-us...@googlegroups.com.
> > To unsubscribe from this group, send email to
> > django-users+unsubscr...@googlegroups.com.
> > For more options, visit this group at
> >http://groups.google.com/group/django-users?hl=en.
>
> --
> Sincerely,
> Michael Schadewww.mschade.me- 815.514.1410

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Re: noob syntax question

[Michael Schade]

(Sorry in advance for the brevity and any typos, I am typing this from
my aging Windows Mobile).

It's quite Django-specific actually. If you take a look at
http://docs.djangoproject.com/en/dev/topics/db/queries/  it says,
"Django also creates API accessors for the "other" side of the
relationship -- the link from the related model to the model that
defines the relationship. For example, a Blog object b has access to a
list of all related Entry objects via the entry_set attribute:
b.entry_set.all()."

Hope that clears things up.

Michael Schade
Spearhead Development LLC

On 6/23/10, Sector7B  wrote:
> Hi,
> In the tutorial 1.
>
> It has this:
> # Give the Poll a couple of Choices. The create call constructs a new
> # choice object, does the INSERT statement, adds the choice to the set
> # of available choices and returns the new Choice object. Django
> creates
> # a set to hold the "other side" of a ForeignKey relation
> # (e.g. a poll's choices) which can be accessed via the API.
>
> and gives these examples:
> # Create three choices.
 p.choice_set.create(choice='Not much', votes=0)
> 
 p.choice_set.create(choice='The sky', votes=0)
> 
 c = p.choice_set.create(choice='Just hacking again', votes=0)
>
> I understand what its doing, but I don't understand where the "_set"
> comes from or where its resolved to.
> Its probably more of a python thing than a django thing, but if
> someone could provide insight, it would be much appreciate.
>
> Thanks,
> -j
>
> --
> You received this message because you are subscribed to the Google Groups
> "Django users" group.
> To post to this group, send email to django-us...@googlegroups.com.
> To unsubscribe from this group, send email to
> django-users+unsubscr...@googlegroups.com.
> For more options, visit this group at
> http://groups.google.com/group/django-users?hl=en.
>
>


-- 
Sincerely,
Michael Schade
www.mschade.me - 815.514.1410

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noob syntax question

[Sector7B]

Hi,
In the tutorial 1.

It has this:
# Give the Poll a couple of Choices. The create call constructs a new
# choice object, does the INSERT statement, adds the choice to the set
# of available choices and returns the new Choice object. Django
creates
# a set to hold the "other side" of a ForeignKey relation
# (e.g. a poll's choices) which can be accessed via the API.

and gives these examples:
# Create three choices.
>>> p.choice_set.create(choice='Not much', votes=0)

>>> p.choice_set.create(choice='The sky', votes=0)

>>> c = p.choice_set.create(choice='Just hacking again', votes=0)

I understand what its doing, but I don't understand where the "_set"
comes from or where its resolved to.
Its probably more of a python thing than a django thing, but if
someone could provide insight, it would be much appreciate.

Thanks,
-j

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