Rails - Aug 2006 - AR: save! doesn't redo object save after child save fails

I have two AR descendant classes, A and B, where A has_many B''s.

I have an action where I create a new (unsaved) A.  It then renders to 
another page that in turn posts to an action that creates several B''s 
that are then associated to A (but not saved yet since A has not been 
saved).

If I call A.save! and there is a problem saving one of the B''s, I 
redisplay my form and prompt the user to fix the data.  Looking at the 
log file, I can see the apparently successful SQL call to save the row 
for A as well as the SQL error for B.

(Note that throughout the process of fixing the B objects, the A object 
is not changed.)

Once the data is fixed, the call to A.save! happens again, and there is 
no INSERT statement for table A.  The save for B fails with a foreign 
key constraint failure (no A row to point to).  There are no A rows in 
the database so this makes sense.

Calling A.new_record? before A.save! shows that the A object thinks it 
is not saved.  However, no INSERT statement for A ever occurs after that 
first, successful save.

I''m guessing that when the first save! call occurs, that the A object 
thinks it saved to the database even though it didn''t (because of the 
child row failures).  Then, later, there is no attempt to re-save the A 
object and the B objects fail to save because there is no A object 
available.  What''s confusing is that A returns "true" to
new_record? and
then no INSERT occurs.

I think I can get around this problem by doing A.save! before I add any 
B''s to it.  But this seems like a bug.

Anybody have any insight into the intricacies of save! with a has_many 
relationship?

Thanks,
Wes

-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
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
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

I ran a test and here''s what I saw.

* 1st call to save!: The INSERT for table A succeeded because the INSERT 
for table B tries to use foreign key id 191 as the foreign key to A. 
The INSERT for table B fails.

* 2nd call to save!: No INSERT statement is executed for A.  The INSERT 
for table B tries to use foreign key id 191 as the foreign key to A. 
The INSERT for table B fails because there is no such A row with id 191.

Not only is the INSERT not being retried for A, but the child rows are 
remembering the original A id and failing for that reason.

WG

-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
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
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

On 8/30/06, Wes Gamble
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
> I ran a test and here''s what I saw.
>
> * 1st call to save!: The INSERT for table A succeeded because the INSERT
> for table B tries to use foreign key id 191 as the foreign key to A.
> The INSERT for table B fails.
>
> * 2nd call to save!: No INSERT statement is executed for A.  The INSERT
> for table B tries to use foreign key id 191 as the foreign key to A.
> The INSERT for table B fails because there is no such A row with id 191.
>
> Not only is the INSERT not being retried for A, but the child rows are
> remembering the original A id and failing for that reason.

The database rollback on a failed save doesn''t rollback your object
also. As
far as it knows, it was inserted fine..

jeremy


--~--~---------~--~----~------------~-------~--~----~
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
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

So then is the correct thing to do to always start from scratch with a 
fresh object to save?

Wes


-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
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
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

On 8/30/06, Wes Gamble
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
> So then is the correct thing to do to always start from scratch with a
> fresh object to save?

Yup - much easier to deal with.  Another option is to check .valid? on
parent and children before saving.

jeremy


--~--~---------~--~----~------------~-------~--~----~
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
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

Jeremy,

Thanks for the responses.  There are a couple of issues here.

1) The database error is happening because the length of one of the 
columns is too long.  Perhaps some validates_length_of is appropriate 
here.

2) But I believe the real problem is that I''m trying to build up my 
object in two different actions that post from 2 different pages.  So 
I''m going to create a separate model object (not to be saved) to act as
a value object to help me build my real object in the 2nd step.

Because I''m trying to build my object across multiple submits,
I''m
saving it to the flash and trying to keep up with its state as errors 
occur in various submits.  And clearly, it isn''t working.

---------------

This all has me thinking about the RESTful thing and I will post about 
that at a higher level soon.

Quickly: Would Rails benefit from the use of form model objects - 
objects whose purpose is to keep track of the state of a form?  (I think 
the answer is yes).

Should we always go down the path of one form <-> one model object no 
matter what (you may have many intermediate steps that you need to do in 
many forms in order to build your object - how is that best 
accomplished)?

Thanks again,
Wes


-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
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
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

On 8/30/06, Wes Gamble
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
> 2) But I believe the real problem is that I''m trying to build up
my
> object in two different actions that post from 2 different pages.  So
> I''m going to create a separate model object (not to be saved) to
act as
> a value object to help me build my real object in the 2nd step.
>
> Because I''m trying to build my object across multiple submits,
I''m
> saving it to the flash and trying to keep up with its state as errors
> occur in various submits.  And clearly, it isn''t working.

An easy approach is to use a candidate record that you save as you go. Then
you can use separate validation rules for the candidate and completed models
- pretty convenient - and easily ''complete'' the candidate when
the wizard''s
done.


Quickly: Would Rails benefit from the use of form model objects
-
> objects whose purpose is to keep track of the state of a form?  (I think
> the answer is yes).

Yes, but I think they would be mis- and over-used. Consider how far Rails
has come without them.


Should we always go down the path of one form <-> one model object
no
> matter what (you may have many intermediate steps that you need to do in
> many forms in order to build your object - how is that best
> accomplished)?

I like the candidate record approach.

jeremy


--~--~---------~--~----~------------~-------~--~----~
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
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---

Candidate record is a nice way to say it.

I can see your point about the mis and over-use of form models - on the 
other hand, aren''t we just misusing regular models and/or views and/or 
controller methods when we use regular models to hold non-trivial form 
state?

In my particular case, I have an upload file step and then a data 
transformation step, and it is totally valid to deal with two objects 
when that much work is going on.

Wes

-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
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
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk
-~----------~----~----~----~------~----~------~--~---