Rails - Aug 2010 - Automatically create one child record when parent record is initially created

Sorry for the newbie question in advance...  I''ve got three models, a
user, site and user_site model.  A site can have many users and a user
can have many sites.  The relationship between these two is stored in
user_site. In my model defs user and sites both have has_many
user_sites statement.  Within my user_sites file, there are two
belongs_to statements, one for user and one for site.  within the What
I''m looking to do is when a user is created initially to automatically
create a record in user_site for a default site (I have it contained
in an instance variable within the user controller).  What I''m not
sure is how to most effectively do this so that the generated id for
user is automatically pulled into the child record in user_site,
basically I''m trying to come up with an efficient method for creating
the user and user_site records.  Any guidance is much appreciated.

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Hi Chris,

On Sun, Aug 29, 2010 at 12:24 PM, Chris
<cdellinger-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Sorry for the newbie question in advance...  I''ve got three
models, a
> user, site and user_site model.  A site can have many users and a user
> can have many sites.  The relationship between these two is stored in
> user_site. In my model defs user and sites both have has_many
> user_sites statement.  Within my user_sites file, there are two
> belongs_to statements, one for user and one for site.  within the What
> I''m looking to do is when a user is created initially to
automatically
> create a record in user_site for a default site (I have it contained
> in an instance variable within the user controller).  What I''m not
> sure is how to most effectively do this so that the generated id for
> user is automatically pulled into the child record in user_site,
> basically I''m trying to come up with an efficient method for
creating
> the user and user_site records.  Any guidance is much appreciated.
Use an after_create filter in your User model to create and populate
the record in user_sites with the user_id.

HTH,
Bill

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How would I handle a failure in that second piece?  Can I put it in
transaction and roll it back?

On Aug 29, 1:31 pm, Bill Walton
<bwalton...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Hi Chris,
>
> On Sun, Aug 29, 2010 at 12:24 PM, Chris
<cdellin...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > Sorry for the newbie question in advance...  I''ve got three
models, a
> > user, site and user_site model.  A site can have many users and a user
> > can have many sites.  The relationship between these two is stored in
> > user_site. In my model defs user and sites both have has_many
> > user_sites statement.  Within my user_sites file, there are two
> > belongs_to statements, one for user and one for site.  within the What
> > I''m looking to do is when a user is created initially to
automatically
> > create a record in user_site for a default site (I have it contained
> > in an instance variable within the user controller).  What
I''m not
> > sure is how to most effectively do this so that the generated id for
> > user is automatically pulled into the child record in user_site,
> > basically I''m trying to come up with an efficient method for
creating
> > the user and user_site records.  Any guidance is much appreciated.
>
> Use an after_create filter in your User model to create and populate
> the record in user_sites with the user_id.
>
> HTH,
> Bill
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On Sun, Aug 29, 2010 at 12:34 PM, Chris
<cdellinger-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> How would I handle a failure in that second piece?  Can I put it in
> transaction and roll it back?
Probabl, though you''d have to throw an exception for a transaction to
be effective.  IIRC, Rails3 has support for creating associated
records built in but I haven''t gotten around to working with 3 and you
didn''t say what version you''re using.

The easiest, most readable thing to do might be to just, in the controller...

if @user.save and @user.user_site
  ....

It''s probably better, though, to move it into the User model''s
after_create (untested code)

after_create :create_default_user_site_rec

def create_default_user_site_rec
  user_site_rec = UserSite.new
  user_site_rec.user_id = self.id
  unless user_site.save
     self.destroy
     false
  end
end

Tricky thing here is I''m not sure off the top of my head if the
failure of the after_create and its returning false will translate
into the save itself returning false.  Sorry I don''t have the time to
run it to ground for you.  Hopefully this will give you some options
to investigate.

Best regards,
Bill

end

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I am using Rails 3.  I got it to work with the following code, but I
haven''t done anything to make it transactional (a user record will get
created even if the second creation fails)

@user = User.new(params[:user])
if @user.save
@user.user_sites << UserSite.create(:site_id => @current_site.id)


On Aug 29, 2:33 pm, Bill Walton
<bwalton...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> On Sun, Aug 29, 2010 at 12:34 PM, Chris
<cdellin...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > How would I handle a failure in that second piece?  Can I put it in
> > transaction and roll it back?
>
> Probabl, though you''d have to throw an exception for a transaction
to
> be effective.  IIRC, Rails3 has support for creating associated
> records built in but I haven''t gotten around to working with 3 and
you
> didn''t say what version you''re using.
>
> The easiest, most readable thing to do might be to just, in the
controller...
>
> if @user.save and @user.user_site
>   ....
>
> It''s probably better, though, to move it into the User
model''s
> after_create (untested code)
>
> after_create :create_default_user_site_rec
>
> def create_default_user_site_rec
>   user_site_rec = UserSite.new
>   user_site_rec.user_id = self.id
>   unless user_site.save
>      self.destroy
>      false
>   end
> end
>
> Tricky thing here is I''m not sure off the top of my head if the
> failure of the after_create and its returning false will translate
> into the save itself returning false.  Sorry I don''t have the time
to
> run it to ground for you.  Hopefully this will give you some options
> to investigate.
>
> Best regards,
> Bill
>
> end
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I am using Rails 3.  I got it to work with the following code, but it
is not currently transactional (if the creation of a UserSite fails
the original user record will still exist in the db).

@user = User.new(params[:user])
if @user.save
   @user.user_sites << UserSite.create(:site_id => @current_site.id)
...
end

While this works I''m not sure if there is a better way to accomplish
this (some Rails goodness I''m not familiar with).  If anyone has an
opinion on it, please let me know.




On Aug 29, 2:33 pm, Bill Walton
<bwalton...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> On Sun, Aug 29, 2010 at 12:34 PM, Chris
<cdellin...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > How would I handle a failure in that second piece?  Can I put it in
> > transaction and roll it back?
>
> Probabl, though you''d have to throw an exception for a transaction
to
> be effective.  IIRC, Rails3 has support for creating associated
> records built in but I haven''t gotten around to working with 3 and
you
> didn''t say what version you''re using.
>
> The easiest, most readable thing to do might be to just, in the
controller...
>
> if @user.save and @user.user_site
>   ....
>
> It''s probably better, though, to move it into the User
model''s
> after_create (untested code)
>
> after_create :create_default_user_site_rec
>
> def create_default_user_site_rec
>   user_site_rec = UserSite.new
>   user_site_rec.user_id = self.id
>   unless user_site.save
>      self.destroy
>      false
>   end
> end
>
> Tricky thing here is I''m not sure off the top of my head if the
> failure of the after_create and its returning false will translate
> into the save itself returning false.  Sorry I don''t have the time
to
> run it to ground for you.  Hopefully this will give you some options
> to investigate.
>
> Best regards,
> Bill
>
> end
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I think I''ve improved on it and made it transactional (please correct
me if I''m wrong).  My new code look as follows:

@user = User.new(params[:user])
@user.user_sites << UserSite.new(:site_id => @current_site.id)
if @user.save
...

I''m using the new method instead of the create on the UserSite
object.  From what I could tell in the docs, when done this way, the
creation of the user (parent record) and the usersite (child record)
are automatically included in a transaction as an atomic unit, so I
shouldn''t have to do anything more.

As I said above please correct me if I''m misunderstanding something
here.



On Aug 29, 8:53 pm, Chris
<cdellin...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> I am using Rails 3.  I got it to work with the following code, but it
> is not currently transactional (if the creation of a UserSite fails
> the original user record will still exist in the db).
>
> @user = User.new(params[:user])
> if @user.save
>    -tENV8f5wrGRQFI55V6+gNQ@public.gmane.org_sites <<
UserSite.create(:site_id => @current_site.id)
> ...
> end
>
> While this works I''m not sure if there is a better way to
accomplish
> this (some Rails goodness I''m not familiar with).  If anyone has
an
> opinion on it, please let me know.
>
> On Aug 29, 2:33 pm, Bill Walton
<bwalton...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
>
>
> > On Sun, Aug 29, 2010 at 12:34 PM, Chris
<cdellin...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > > How would I handle a failure in that second piece?  Can I put it
in
> > > transaction and roll it back?
>
> > Probabl, though you''d have to throw an exception for a
transaction to
> > be effective.  IIRC, Rails3 has support for creating associated
> > records built in but I haven''t gotten around to working with
3 and you
> > didn''t say what version you''re using.
>
> > The easiest, most readable thing to do might be to just, in the
controller...
>
> > if @user.save and @user.user_site
> >   ....
>
> > It''s probably better, though, to move it into the User
model''s
> > after_create (untested code)
>
> > after_create :create_default_user_site_rec
>
> > def create_default_user_site_rec
> >   user_site_rec = UserSite.new
> >   user_site_rec.user_id = self.id
> >   unless user_site.save
> >      self.destroy
> >      false
> >   end
> > end
>
> > Tricky thing here is I''m not sure off the top of my head if
the
> > failure of the after_create and its returning false will translate
> > into the save itself returning false.  Sorry I don''t have the
time to
> > run it to ground for you.  Hopefully this will give you some options
> > to investigate.
>
> > Best regards,
> > Bill
>
> > end
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