Rails - Jun 2010 - How do you update one object of a has_many :through relationship

Hi guys.

How do you update nested attributes for one object of a
has_many :through relationship? So I have an entity model and this
model can have many fact_values. The difference between fact and
fact_value is that the latter has an extra value attribute. This is
because facts can be common among many entities, but each entity can
have its own unique value for a specific fact. So my models are the
following:

class Entity
  has_many :fact_values
  has_many :facts, :through => :fact_values
end

class FactValue
  belongs_to :entity
  belongs_to :fact
end

class Fact
  has_many :fact_values
  has_many :entities, :through => :fact_values
end

Now I''ve specified that Entity
accepts_nested_attributes_for :fact_values. But I want it to accept
nested attributes for a single (pre-defined) fact_value and update
only that fact_value. The way I''m going about it right now is to have
a virtual attribute in my Entity model representing that one
fact_value and update that fact_value in the entity controller. I''m
wondering if there is any automatic way to accomplish what I''m trying
to do?

Thanks!

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On Jun 14, 7:55 am, Ali
<ali.akhtarz...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> I want it to accept nested attributes for a single (pre-defined)
> fact_value and update only that fact_value
I''m not sure exactly what the problem is. If you only want to update
one object, you only put that object in the fields_for(:fact_values)
part of the form.
If you''re worried about the wrong object being created/updated through
accepts_nested_attributes, then the :reject_if can enable you to add
validation.

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On Mon, Jun 14, 2010 at 1:55 AM, Ali
<ali.akhtarzada-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Hi guys.
>
> How do you update nested attributes for one object of a
> has_many :through relationship? So I have an entity model and this
> model can have many fact_values. The difference between fact and
> fact_value is that the latter has an extra value attribute. This is
> because facts can be common among many entities, but each entity can
> have its own unique value for a specific fact. So my models are the
> following:
>
> class Entity
>  has_many :fact_values
>  has_many :facts, :through => :fact_values
> end
>
> class FactValue
>  belongs_to :entity
>  belongs_to :fact
> end
>
> class Fact
>  has_many :fact_values
>  has_many :entities, :through => :fact_values
> end
>
> Now I''ve specified that Entity
> accepts_nested_attributes_for :fact_values. But I want it to accept
> nested attributes for a single (pre-defined) fact_value and update
> only that fact_value. The way I''m going about it right now is to
have
> a virtual attribute in my Entity model representing that one
> fact_value and update that fact_value in the entity controller.
I''m
> wondering if there is any automatic way to accomplish what I''m
trying
> to do?
Perhaps something along the lines of

class Entity

  has_many :fact_values
  has_many :facts, :through => :fact_values
  belongs_to :anointed_fact_value

   accepts_nested_attributes_for :fact_values, :reject_if =>
:not_updatable_fact_value

   def not_updatable_fact_value(attrs)
      attrs[:id] != anointed_fact_value_id
   end
end



-- 
Rick DeNatale

Blog: http://talklikeaduck.denhaven2.com/
Github: http://github.com/rubyredrick
Twitter: @RickDeNatale
WWR: http://www.workingwithrails.com/person/9021-rick-denatale
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I''m using formtastic, I see that it seems simple enough with the
standard
rails forms. I suppose I can ask on a formtastic gorup to see what they say.

Thanks

On Tue, Jun 15, 2010 at 1:20 AM, Rick DeNatale
<rick.denatale-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>wrote:
> On Mon, Jun 14, 2010 at 1:55 AM, Ali
<ali.akhtarzada-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > Hi guys.
> >
> > How do you update nested attributes for one object of a
> > has_many :through relationship? So I have an entity model and this
> > model can have many fact_values. The difference between fact and
> > fact_value is that the latter has an extra value attribute. This is
> > because facts can be common among many entities, but each entity can
> > have its own unique value for a specific fact. So my models are the
> > following:
> >
> > class Entity
> >  has_many :fact_values
> >  has_many :facts, :through => :fact_values
> > end
> >
> > class FactValue
> >  belongs_to :entity
> >  belongs_to :fact
> > end
> >
> > class Fact
> >  has_many :fact_values
> >  has_many :entities, :through => :fact_values
> > end
> >
> > Now I''ve specified that Entity
> > accepts_nested_attributes_for :fact_values. But I want it to accept
> > nested attributes for a single (pre-defined) fact_value and update
> > only that fact_value. The way I''m going about it right now is
to have
> > a virtual attribute in my Entity model representing that one
> > fact_value and update that fact_value in the entity controller.
I''m
> > wondering if there is any automatic way to accomplish what
I''m trying
> > to do?
>
> Perhaps something along the lines of
>
> class Entity
>
>  has_many :fact_values
>  has_many :facts, :through => :fact_values
>   belongs_to :anointed_fact_value
>
>   accepts_nested_attributes_for :fact_values, :reject_if =>
> :not_updatable_fact_value
>
>   def not_updatable_fact_value(attrs)
>      attrs[:id] != anointed_fact_value_id
>   end
> end
>
>
>
> --
> Rick DeNatale
>
> Blog: http://talklikeaduck.denhaven2.com/
> Github: http://github.com/rubyredrick
> Twitter: @RickDeNatale
> WWR: http://www.workingwithrails.com/person/9021-rick-denatale
> LinkedIn: http://www.linkedin.com/in/rickdenatale
>
> --
> You received this message because you are subscribed to the Google Groups
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>
rubyonrails-talk+unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org<rubyonrails-talk%2Bunsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org>
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>
>
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