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Vaishal Sheth

2006-Apr-06 17:52 UTC

[Rails] Record retrieval in Many-to-many using :through not working

Hello,

I get an error while retrieving records from the following model structure.

Tables
foods - id, food
foodallergies - food_id, symptom_id, a few other columns
symptoms - id, symptom

Models
class Food < ActiveRecord::Base
  has_many :foodallergies
  has_many :symptoms, :through => :foodallergies
end

class Symptom < ActiveRecord::Base
  has_many :foodallergies
  has_many :foods, :through => :foodallergies
end

class Foodallergy < ActiveRecord::Base
  belongs_to :foods
  belongs_to :symptoms
end

In the console, when I do
f = Food.find(:first), the first food item is returned. I can also retrieve
a symptom that way directly from the Symptom model.

But, this does not work.

f = Food.find(:first)
f.symptoms

f.symptoms generates an error which looks like this

?> f = Food.find(:first)
=> #<Food:0x39d30b0 @attributes={"food"=>"pizza",
"id"=>"29"}>>> s = Symptom.find(:first)=> #<Symptom:0x39d2e10 @attributes={"id"=>"21",
"symptom"=>"migraine"}>>> f.symptomsNameError: c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.0
/lib/active_support
/dependencies.rb:89:in `const_missing'': uninitialized constant Symptoms
        from c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0
/lib/active_recor
d/base.rb:1242:in `compute_type''
        from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.0
/lib/active_suppo
rt/dependencies.rb:120:in `const_missing''
        from c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.0
/lib/active_suppo
rt/dependencies.rb:122:in `const_missing''
        from (eval):1:in `compute_type''
        from c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0
/lib/active_recor
d/reflection.rb:112:in `klass''
        from c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0
/lib/active_recor
d/associations/has_many_through_association.rb:54:in `find_target''
        from c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0
/lib/active_recor
d/associations/association_proxy.rb:116:in `load_target''
        from c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0
/lib/active_recor
d/associations/association_proxy.rb:109:in `method_missing''
        from c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0
/lib/active_recor
d/associations/has_many_through_association.rb:47:in `method_missing''
        from c:/ruby/lib/ruby/1.8/irb.rb:298:in `output_value''
        from c:/ruby/lib/ruby/1.8/irb.rb:151:in `eval_input''
        from c:/ruby/lib/ruby/1.8/irb.rb:259:in `signal_status''
        from c:/ruby/lib/ruby/1.8/irb.rb:147:in `eval_input''
        from c:/ruby/lib/ruby/1.8/irb.rb:146:in `eval_input''
        from c:/ruby/lib/ruby/1.8/irb.rb:70:in `start''
        from c:/ruby/lib/ruby/1.8/irb.rb:69:in `start''
        from c:/ruby/bin/irb.bat:20>>
>From all the examples I have seen so far, f.symptoms should work.  And yes,I have the right foreign keys values in foodallergies table.

Any ideas?

Vaishal
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njmacinnes@gmail.com

2006-Apr-06 18:14 UTC

head link

[Rails] Record retrieval in Many-to-many using :through not working

One one thing is connected through another, it should belong to it.
I''m not aware that you can do it the other way around... but it might
be possible. For example:

Models
class Food < ActiveRecord::Base
  belongs_to :foodallergies
  has_many :symptoms, :through => :foodallergies
end


On 06/04/06, Vaishal Sheth <vpsheth@gmail.com>
wrote:> Hello,
>
> I get an error while retrieving records from the following model structure.
>
> Tables
> foods - id, food
> foodallergies - food_id, symptom_id, a few other columns
> symptoms - id, symptom
>
> Models
> class Food < ActiveRecord::Base
>   has_many :foodallergies
>   has_many :symptoms, :through => :foodallergies
> end
>
> class Symptom < ActiveRecord::Base
>   has_many :foodallergies
>   has_many :foods, :through => :foodallergies
> end
>
> class Foodallergy < ActiveRecord::Base
>   belongs_to :foods
>   belongs_to :symptoms
> end
>
> In the console, when I do
> f = Food.find(:first), the first food item is returned. I can also retrieve
> a symptom that way directly from the Symptom model.
>
> But, this does not work.
>
> f = Food.find (:first)
> f.symptoms
>
> f.symptoms generates an error which looks like this
>
> ?> f = Food.find(:first)
> => #<Food:0x39d30b0
@attributes={"food"=>"pizza",
"id"=>"29"}>
> >> s = Symptom.find(:first)
> => #<Symptom:0x39d2e10
@attributes={"id"=>"21",
"symptom"=>"migraine"}>
> >> f.symptoms
> NameError: c:/ruby/lib/ruby/gems/1.8/gems/activesupport-
> 1.3.0/lib/active_support
> /dependencies.rb:89:in `const_missing'': uninitialized constant
Symptoms
>         from
> c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0/lib/active_recor
> d/base.rb:1242:in `compute_type''
>         from
> c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.0/lib/active_suppo
> rt/dependencies.rb:120:in `const_missing''
>         from
> c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.0/lib/active_suppo
> rt/dependencies.rb:122:in `const_missing''
>         from (eval):1:in `compute_type''
>         from
> c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0/lib/active_recor
> d/reflection.rb:112:in `klass''
>         from c:/ruby/lib/ruby/gems/1.8/gems/activerecord-
> 1.14.0/lib/active_recor
> d/associations/has_many_through_association.rb:54:in
> `find_target''
>         from
> c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0/lib/active_recor
> d/associations/association_proxy.rb:116:in `load_target''
>         from
> c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0/lib/active_recor
> d/associations/association_proxy.rb:109:in `method_missing''
>         from
> c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0/lib/active_recor
> d/associations/has_many_through_association.rb:47:in
> `method_missing''
>         from c:/ruby/lib/ruby/1.8/irb.rb:298:in
> `output_value''
>         from c:/ruby/lib/ruby/1.8/irb.rb:151:in
> `eval_input''
>         from c:/ruby/lib/ruby/1.8/irb.rb:259:in
> `signal_status''
>         from c:/ruby/lib/ruby/1.8/irb.rb:147:in
> `eval_input''
>         from c:/ruby/lib/ruby/1.8/irb.rb:146:in
> `eval_input''
>         from c:/ruby/lib/ruby/1.8/irb.rb:70:in `start''
>         from c:/ruby/lib/ruby/1.8/irb.rb:69:in `start''
>         from c:/ruby/bin/irb.bat:20>>
>
> From all the examples I have seen so far, f.symptoms should work.  And yes,
> I have the right foreign keys values in foodallergies table.
>
> Any ideas?
>
> Vaishal
>
>
>
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>

Vaishal Sheth

2006-Apr-06 18:27 UTC

head link

[Rails] Record retrieval in Many-to-many using :through not working

No, that''s not the way to set a many-to-many using through.

I am using this
http://media.rubyonrails.org/presentations/pursuitofbeauty.pdf (Pg 14)
example by DHH as a guide and it seems I am doing it right.

But I am doing something wrong too...I am not sure what.

On 4/6/06, njmacinnes@gmail.com <njmacinnes@gmail.com>
wrote:>
> One one thing is connected through another, it should belong to it.
> I''m not aware that you can do it the other way around... but it
might
> be possible. For example:
>
> Models
> class Food < ActiveRecord::Base
>   belongs_to :foodallergies
>   has_many :symptoms, :through => :foodallergies
> end
>
>
> On 06/04/06, Vaishal Sheth <vpsheth@gmail.com> wrote:
> > Hello,
> >
> > I get an error while retrieving records from the following model
> structure.
> >
> > Tables
> > foods - id, food
> > foodallergies - food_id, symptom_id, a few other columns
> > symptoms - id, symptom
> >
> > Models
> > class Food < ActiveRecord::Base
> >   has_many :foodallergies
> >   has_many :symptoms, :through => :foodallergies
> > end
> >
> > class Symptom < ActiveRecord::Base
> >   has_many :foodallergies
> >   has_many :foods, :through => :foodallergies
> > end
> >
> > class Foodallergy < ActiveRecord::Base
> >   belongs_to :foods
> >   belongs_to :symptoms
> > end
> >
> > In the console, when I do
> > f = Food.find(:first), the first food item is returned. I can also
> retrieve
> > a symptom that way directly from the Symptom model.
> >
> > But, this does not work.
> >
> > f = Food.find (:first)
> > f.symptoms
> >
> > f.symptoms generates an error which looks like this
> >
> > ?> f = Food.find(:first)
> > => #<Food:0x39d30b0
@attributes={"food"=>"pizza",
"id"=>"29"}>
> > >> s = Symptom.find(:first)
> > => #<Symptom:0x39d2e10
@attributes={"id"=>"21",
"symptom"=>"migraine"}>
> > >> f.symptoms
> > NameError: c:/ruby/lib/ruby/gems/1.8/gems/activesupport-
> > 1.3.0/lib/active_support
> > /dependencies.rb:89:in `const_missing'': uninitialized
constant Symptoms
> >         from
> > c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0/lib/active_recor
> > d/base.rb:1242:in `compute_type''
> >         from
> > c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.0/lib/active_suppo
> > rt/dependencies.rb:120:in `const_missing''
> >         from
> > c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.0/lib/active_suppo
> > rt/dependencies.rb:122:in `const_missing''
> >         from (eval):1:in `compute_type''
> >         from
> > c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0/lib/active_recor
> > d/reflection.rb:112:in `klass''
> >         from c:/ruby/lib/ruby/gems/1.8/gems/activerecord-
> > 1.14.0/lib/active_recor
> > d/associations/has_many_through_association.rb:54:in
> > `find_target''
> >         from
> > c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0/lib/active_recor
> > d/associations/association_proxy.rb:116:in `load_target''
> >         from
> > c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0/lib/active_recor
> > d/associations/association_proxy.rb:109:in `method_missing''
> >         from
> > c:/ruby/lib/ruby/gems/1.8/gems/activerecord-1.14.0/lib/active_recor
> > d/associations/has_many_through_association.rb:47:in
> > `method_missing''
> >         from c:/ruby/lib/ruby/1.8/irb.rb:298:in
> > `output_value''
> >         from c:/ruby/lib/ruby/1.8/irb.rb:151:in
> > `eval_input''
> >         from c:/ruby/lib/ruby/1.8/irb.rb:259:in
> > `signal_status''
> >         from c:/ruby/lib/ruby/1.8/irb.rb:147:in
> > `eval_input''
> >         from c:/ruby/lib/ruby/1.8/irb.rb:146:in
> > `eval_input''
> >         from c:/ruby/lib/ruby/1.8/irb.rb:70:in `start''
> >         from c:/ruby/lib/ruby/1.8/irb.rb:69:in `start''
> >         from c:/ruby/bin/irb.bat:20>>
> >
> > From all the examples I have seen so far, f.symptoms should work.  And
> yes,
> > I have the right foreign keys values in foodallergies table.
> >
> > Any ideas?
> >
> > Vaishal
> >
> >
> >
> >
> > _______________________________________________
> > Rails mailing list
> > Rails@lists.rubyonrails.org
> > http://lists.rubyonrails.org/mailman/listinfo/rails
> >
> >
> >
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
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Mark Reginald James

2006-Apr-06 19:41 UTC

head link

[Rails] Re: Record retrieval in Many-to-many using :through not working

Vaishal Sheth wrote:
> class Foodallergy < ActiveRecord::Base
>   belongs_to :foods
>   belongs_to :symptoms
> end
> ...
> NameError: c:/ruby/lib/ruby/gems/1.8/gems/activesupport- 
> 1.3.0/lib/active_support
> /dependencies.rb:89:in `const_missing'': uninitialized constant
Symptoms
Use the singular symbols :food and :symptom for your belong_tos.


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

Vaishal Sheth

2006-Apr-06 19:59 UTC

head link

[Rails] Re: Record retrieval in Many-to-many using :through not working

Thanks a LOT Mark!!

I could have looked at it all night and never caught that.

On 4/7/06, Mark Reginald James <mrj@bigpond.net.au>
wrote:>
> Vaishal Sheth wrote:
>
> > class Foodallergy < ActiveRecord::Base
> >   belongs_to :foods
> >   belongs_to :symptoms
> > end
> > ...
> > NameError: c:/ruby/lib/ruby/gems/1.8/gems/activesupport-
> > 1.3.0/lib/active_support
> > /dependencies.rb:89:in `const_missing'': uninitialized
constant Symptoms
>
> Use the singular symbols :food and :symptom for your belong_tos.
>
>
> --
> We develop, watch us RoR, in numbers too big to ignore.
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
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