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bertramseiner-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org

2007-Nov-21 19:54 UTC

Strange behavior in HABTM

Hello,

i have here some Problems to add an Item to an has_and_belongs_to_many
association. I have a class, that holds Bug entries it is connected to
an Table that holds some tags. Now ive defined a method which adds a
tag to the bug. When i do this on a console it works correctly.
I load an bug entry from db and load an tag item from other table.
When i add the tag to bug.tags and save the bug is there an new entry
in the bugs_tags table. When i do the same in my method it doesnt
work.

My Method to add some tag:
  def add_tag
    bug = Bug.find params[:id]
    tag = Tag.find_by_name params[:tagname]
    bug.tags << tag
    if tag.save
      flash[:notice] = _("Tag successfully added")
    else
      flash[:notice] = _("Tag could not be added")
    end
    redirect_to :action => "list"
  end

When i try to add an tga i get the following errorpage
Mysql::Error: Duplicate entry ''3'' for key 1: INSERT INTO
bugs_tags
(`tag_id`, `id`, `bug_id`) VALUES (3, 3, 9)

The problem is, that the id gets not incremented from Rails. The first
entry is correct but when i try to add an second tag i get always this
error. What could it be?

Thanks for any help.
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Jason Roelofs

2007-Nov-21 20:19 UTC

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Re: Strange behavior in HABTM

On Nov 21, 2007 2:54 PM, bertramseiner-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org
<
bertramseiner-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote:
>
> Hello,
>
> i have here some Problems to add an Item to an has_and_belongs_to_many
> association. I have a class, that holds Bug entries it is connected to
> an Table that holds some tags. Now ive defined a method which adds a
> tag to the bug. When i do this on a console it works correctly.
> I load an bug entry from db and load an tag item from other table.
> When i add the tag to bug.tags and save the bug is there an new entry
> in the bugs_tags table. When i do the same in my method it doesnt
> work.
>
> My Method to add some tag:
>  def add_tag
>    bug = Bug.find params[:id]
>    tag = Tag.find_by_name params[:tagname]
>    bug.tags << tag
>    if tag.save
>      flash[:notice] = _("Tag successfully added")
>    else
>      flash[:notice] = _("Tag could not be added")
>    end
>    redirect_to :action => "list"
>  end
>
> When i try to add an tga i get the following errorpage
> Mysql::Error: Duplicate entry ''3'' for key 1: INSERT INTO
bugs_tags
> (`tag_id`, `id`, `bug_id`) VALUES (3, 3, 9)
>
> The problem is, that the id gets not incremented from Rails. The first
> entry is correct but when i try to add an second tag i get always this
> error. What could it be?
>
> Thanks for any help.
>
Try bug.save instead of tag.save?

Do you have a :unique => true on the tag_id field?

Jason

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bertramseiner-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org

2007-Nov-22 08:34 UTC

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Re: Strange behavior in HABTM

> > My Method to add some tag:
> >  def add_tag
> >    bug = Bug.find params[:id]
> >    tag = Tag.find_by_name params[:tagname]
> >    bug.tags << tag
> >    if tag.save
> >      flash[:notice] = _("Tag successfully added")
> >    else
> >      flash[:notice] = _("Tag could not be added")
> >    end
> >    redirect_to :action => "list"
> >  end
>
> > When i try to add an tga i get the following errorpage
> > Mysql::Error: Duplicate entry ''3'' for key 1: INSERT
INTO bugs_tags
> > (`tag_id`, `id`, `bug_id`) VALUES (3, 3, 9)
>
> > The problem is, that the id gets not incremented from Rails. The first
> > entry is correct but when i try to add an second tag i get always this
> > error. What could it be?
>
> > Thanks for any help.
>
> Try bug.save instead of tag.save?
>
> Do you have a :unique => true on the tag_id field?
>
> JasonHello,

ive tried both ways. The Fields in table are not :unique because its
an n to m association the only unique field is id which is the primary
key of this table. But that field  is created by the migration itself.
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Elinor Bakker

2007-Nov-22 11:59 UTC

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Re: Strange behavior in HABTM

bertramseiner-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org
wrote:> 
> My Method to add some tag:
>   def add_tag
>     bug = Bug.find params[:id]
>     tag = Tag.find_by_name params[:tagname]
>     bug.tags << tag
>     if tag.save
>       flash[:notice] = _("Tag successfully added")
>     else
>       flash[:notice] = _("Tag could not be added")
>     end
>     redirect_to :action => "list"
>   end
> The problem is, that the id gets not incremented from Rails. The first
> entry is correct but when i try to add an second tag i get always this
> error. What could it be?
> 
> Thanks for any help.
Dear bertram,

I am a bit of a n00b, but yesterday I spend on HABTM behaviours in 
Rails. I notice that your join table has an id field. I understand that 
when you use HABTM behaviors, the join table should only contain a pair 
of two foreign keys. In my opinion this is also correct in 
normalization. Perhaps you should delete the id field (and make the 
uniqueness of the pair of two foreign key your primary key).

You can create a join table without id like this:

create_table :employees_shifts, :id => false do |t|
      t.column :employee_id, :integer
      t.column :shift_id, :integer
    end

Also, this line:

bug.tags << tag

Should be in the if statement, so the record will not be added if it 
could not be validated.

I hope you find this useful.

Elinor

-- 
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bertramseiner-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org

2007-Nov-22 17:54 UTC

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Re: Strange behavior in HABTM

Dear Elinor,

thanks for zour help. I tried it and it works now.
I had no idea how to say rails that it has not to create an id field
in that table. But i meant it must be something else ;)
In my Rails book that shows all examples by creating the db tables by
hand there is also no id field in the table =)

Bertram

On 22 Nov., 12:59, Elinor Bakker
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:> bertramsei...-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org wrote:
>
> > My Method to add some tag:
> >   def add_tag
> >     bug = Bug.find params[:id]
> >     tag = Tag.find_by_name params[:tagname]
> >     bug.tags << tag
> >     if tag.save
> >       flash[:notice] = _("Tag successfully added")
> >     else
> >       flash[:notice] = _("Tag could not be added")
> >     end
> >     redirect_to :action => "list"
> >   end
> > The problem is, that the id gets not incremented from Rails. The first
> > entry is correct but when i try to add an second tag i get always this
> > error. What could it be?
>
> > Thanks for any help.
>
> Dear bertram,
>
> I am a bit of a n00b, but yesterday I spend on HABTM behaviours in
> Rails. I notice that your join table has an id field. I understand that
> when you use HABTM behaviors, the join table should only contain a pair
> of two foreign keys. In my opinion this is also correct in
> normalization. Perhaps you should delete the id field (and make the
> uniqueness of the pair of two foreign key your primary key).
>
> You can create a join table without id like this:
>
> create_table :employees_shifts, :id => false do |t|
>       t.column :employee_id, :integer
>       t.column :shift_id, :integer
>     end
>
> Also, this line:
>
> bug.tags << tag
>
> Should be in the if statement, so the record will not be added if it
> could not be validated.
>
> I hope you find this useful.
>
> Elinor
>
> --
> Posted viahttp://www.ruby-forum.com/.--~--~---------~--~----~------------~-------~--~----~
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Rails - Nov 2007 - Strange behavior in HABTM

Strange behavior in HABTM

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Re: Strange behavior in HABTM