Rails - Jun 2006 - When saving parent fails, children will still be updated

Hi all,

When submitting a master/detail form I first want to handle the children 
before saving the parent.
There are has_many and belongs_to relations between the parent and the 
children, so I can edit the children using (psuedo-)code like:
child.destroy for deleting, child.update_attributes for updating and 
@parent.children.push(child) for adding child-records.
I update the parent by using:
if @parent.update_attributes(params[:parent])
  flash[:notice] = ''Parent was successfully updated.''
  redirect_to(:action => "list")
else
  render :action => ''edit''
end # if

The problem I''m facing at the moment is that when updating the parent 
fails, the chances made to the children are still saved. I tried to 
include the code in a transaction:
Parent.transaction do
# all code
end

but this makes no difference.

What am I doing wrong? Hope someone can help me out on this.

Thanks in advance,

Patrick

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

Patrick Baselier wrote:
> When submitting a master/detail form I first want to handle the children 
> before saving the parent.
> There are has_many and belongs_to relations between the parent and the 
> children, so I can edit the children using (psuedo-)code like:
> child.destroy for deleting, child.update_attributes for updating and 
> @parent.children.push(child) for adding child-records.
> I update the parent by using:
> if @parent.update_attributes(params[:parent])
>   flash[:notice] = ''Parent was successfully updated.''
>   redirect_to(:action => "list")
> else
>   render :action => ''edit''
> end # if
> 
> The problem I''m facing at the moment is that when updating the
parent
> fails, the chances made to the children are still saved. I tried to 
> include the code in a transaction:
> Parent.transaction do
> # all code
> end
> 
> but this makes no difference.
You have to raise an exception to rollback a transaction.
So you must code something like:

begin
   Parent.transaction do
     # update children
     @parent.attributes = params[:parent]
     @parent.save!
     flash[:notice] = ''Parent was successfully updated.''
     redirect_to :action => "list"
   end
rescue
    render :action => ''edit''
end


To avoid a transaction you''d have to check everything for
validity before you start any saving, and then hope there''s
no database errors.

-- 
We develop, watch us RoR, in numbers too big to ignore.

On 6/13/06, Patrick Baselier <patrick.baselier@gmail.com>
wrote:
> Hi all,
>
> When submitting a master/detail form I first want to handle the children
> before saving the parent.
*snip*
> The problem I''m facing at the moment is that when updating the
parent
> fails, the chances made to the children are still saved. I tried to
> include the code in a transaction:
> Parent.transaction do
> # all code
> end
>
> but this makes no difference.
>
> What am I doing wrong? Hope someone can help me out on this.
Which db are you using? A certain popular ''database''
doesn''t enable
transactions by default.

Isak

Isak Hansen wrote:
> Which db are you using?
I''m using mySQL 4.1 and created InnoDB tables. I still have to try Mark
Reginald James'' suggestion, I think that''ll do it. Let you
know later
today.


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

Mark Reginald James wrote:
> You have to raise an exception to rollback a transaction.
Thanks Mark, I replace my code and it works.

Great!

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