Rails - Jul 2011 - belongs_to --- has_many should update automatically?

On p. 299 of the current Rails book it says that "Active Record takes
care of saving all the dependent child rows when you save a parent
row."  So, when I add a row to the table that has "belongs_to" in
its
model, shouldn''t the table with the "has_many" be updated
with data
from the foreign key?  If not, how do I save data from a form into
more than one table? (And, maybe unfairly expanding into a second
question, how could I put fields from multiple tables on a web page so
that when it is filled out the values will go into various tables?)
In both of these forms of questions I''m trying to get an answer to how
data that will go into multiple tables can come from one web page.  I
hope my statement of the problem isn''t too confusing.
        Thanks,
            Barney

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It''s a common problem and there''s isn''t one answer.

I''ll give you three:

1) If the objects have relationships to eachother, specify
accepts_nested_attribtues_for in your models and then let active record do its
thing (what you described in your post works only if you do
accepts_nested_attribtues_for in your models). If class Apple has_one :orange
and also accepts_nested_attributes_for :orange, you can have fields on your form
like this:

text_field_tag "apple[orange][skin]", "peeled"


2) Hack together a single form that contains parameters from two different
objects. On the controller, you''ll get params[:apple] and
params[:orange]

You can''t use form_for as a resource oriented form_for, but you can use
form_for and just give the fields custom names that are scoped to the objects
you want to scope

text_field_tag "apple[variety]", "golden delicious"
text_field_tag "orange[skin]", "peeled"

In your controller, you would do something like this

@apple.update_attributes(params[:apple])
@orange.update_attributes(params[:orange])


That''s a little hacky, to be frank. If you were doing this with two
distinct objects I might do a quick hack like that, but it''s not
scalable.


3) Take the example of a Registration process. Let''s say you want to
register a camper for summer camp (nice July-appropriate example). One thing you
can do is create a Registration object that synthesizes all the other things
together. If your Registration object itself has database records, you can use
something like strategy #1 above. But, keep in mind that your Registration
object doesn''t have to be ActiveRecord (or have database records) at
all. Experiment with (or just think about) making a Ruby model object that has
no active record component.

In that paradigm, the Ruby model object (that does not inherit from active
record and also does not have database records), represents the transaction. You
won''t keep it around after the controller it done (because it will be
gone from memory after the execute is done). But you can instantiate it, work
with it, write business logic on it, pass it messages (call methods) and let it
update other objects in your system.

That would be a more globalized strategy if say, you wanted to submit one form
and have it touch 5 different objects.

-Jason
 




On Jul 14, 2011, at 4:47 PM, Barney wrote:
> On p. 299 of the current Rails book it says that "Active Record takes
> care of saving all the dependent child rows when you save a parent
> row."  So, when I add a row to the table that has
"belongs_to" in its
> model, shouldn''t the table with the "has_many" be
updated with data
> from the foreign key?  If not, how do I save data from a form into
> more than one table? (And, maybe unfairly expanding into a second
> question, how could I put fields from multiple tables on a web page so
> that when it is filled out the values will go into various tables?)
> In both of these forms of questions I''m trying to get an answer to
how
> data that will go into multiple tables can come from one web page.  I
> hope my statement of the problem isn''t too confusing.
>        Thanks,
>            Barney
> 
> -- 
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> 
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Thanks Jason,
     The first option sounds like it would be the most consistent with
Rails so I''ll read up on accepts_nested_attributes_for and try to make
that work.
               Barney


On Jul 14, 5:15 pm, Jason Fleetwood-Boldt
<t...-eJ8lBn5LdNBhbmWW9KSYcQ@public.gmane.org>
wrote:
> It''s a common problem and there''s isn''t one
answer.
>
> I''ll give you three:
>
> 1) If the objects have relationships to eachother, specify
accepts_nested_attribtues_for in your models and then let active record do its
thing (what you described in your post works only if you do
accepts_nested_attribtues_for in your models). If class Apple has_one :orange
and also accepts_nested_attributes_for :orange, you can have fields on your form
like this:
>
> text_field_tag "apple[orange][skin]", "peeled"
>
> 2) Hack together a single form that contains parameters from two different
objects. On the controller, you''ll get params[:apple] and
params[:orange]
>
> You can''t use form_for as a resource oriented form_for, but you
can use form_for and just give the fields custom names that are scoped to the
objects you want to scope
>
> text_field_tag "apple[variety]", "golden delicious"
> text_field_tag "orange[skin]", "peeled"
>
> In your controller, you would do something like this
>
> @apple.update_attributes(params[:apple])
> @orange.update_attributes(params[:orange])
>
> That''s a little hacky, to be frank. If you were doing this with
two distinct objects I might do a quick hack like that, but it''s not
scalable.
>
> 3) Take the example of a Registration process. Let''s say you want
to register a camper for summer camp (nice July-appropriate example). One thing
you can do is create a Registration object that synthesizes all the other things
together. If your Registration object itself has database records, you can use
something like strategy #1 above. But, keep in mind that your Registration
object doesn''t have to be ActiveRecord (or have database records) at
all. Experiment with (or just think about) making a Ruby model object that has
no active record component.
>
> In that paradigm, the Ruby model object (that does not inherit from active
record and also does not have database records), represents the transaction. You
won''t keep it around after the controller it done (because it will be
gone from memory after the execute is done). But you can instantiate it, work
with it, write business logic on it, pass it messages (call methods) and let it
update other objects in your system.
>
> That would be a more globalized strategy if say, you wanted to submit one
form and have it touch 5 different objects.
>
> -Jason
>
> On Jul 14, 2011, at 4:47 PM, Barney wrote:
>
> > On p. 299 of the current Rails book it says that "Active Record
takes
> > care of saving all the dependent child rows when you save a parent
> > row."  So, when I add a row to the table that has
"belongs_to" in its
> > model, shouldn''t the table with the "has_many" be
updated with data
> > from the foreign key?  If not, how do I save data from a form into
> > more than one table? (And, maybe unfairly expanding into a second
> > question, how could I put fields from multiple tables on a web page so
> > that when it is filled out the values will go into various tables?)
> > In both of these forms of questions I''m trying to get an
answer to how
> > data that will go into multiple tables can come from one web page.  I
> > hope my statement of the problem isn''t too confusing.
> >        Thanks,
> >            Barney
>
> > --
> > You received this message because you are subscribed to the Google
Groups "Ruby on Rails: Talk" group.
> > To post to this group, send email to
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