Hey Marco,
Thanks a lot for you quick response.
So, I tried to change my models to use only *has_many* and *belongs_to*,
instead of *has_and_belongs_to_many*.
I also added the foreign key to material_id:
class Composition < ActiveRecord::Base
belongs_to :material, :class_name => "Material", :foreign_key =>
'material_id'
belongs_to :product
end
class Material < ActiveRecord::Base
has_many :compositions
has_many :products, through: :composition
end
class Product < ActiveRecord::Base
has_many :compositions
has_many :materials, through: :composition
end
On rails console, I can run fine:
@p = Product.first
@p.compositions
@p.compositions.includes(:material)
But this last one returns me only the items I already have on composition,
not the actual material attributes.
@p.compositions.includes(:material)
Composition Load (0.5ms) SELECT "compositions".* FROM "compositions"
WHERE "compositions"."product_id" = $1 [["product_id", 1]]
Material Load (0.7ms) SELECT "materials".* FROM "materials" WHERE
"materials"."id" IN (1, 2)
=> #<ActiveRecord::AssociationRelation [#<Composition id: 5, product_id: 1,
material_id: 1, material_quantity: 3, created_at: "2015-03-30 05:20:27",
updated_at: "2015-03-30 05:20:27">, #<Composition id: 6, product_id: 1,
material_id: 2, material_quantity: 2, created_at: "2015-03-30 05:20:27",
updated_at: "2015-03-30 05:20:27">]>
I would like to also get the material names from Material model.
How do I get them using this approach?
Thanks again,
Leandro
On Monday, March 30, 2015 at 10:58:52 AM UTC-3, Marco Antonio wrote:
>
> Now I see that you have the quantity inside your compositions table and
> you probably need that.
>
> You can use the code you have in your controller normally with the changes
> mentioned in my last e-mail.
>
> *Marco Almeida*
> about.me/marcoafilho
> +45 31 65 28 84
>
> On Mon, Mar 30, 2015 at 3:53 PM, Marco Antonio Almeida <marco...@gmail.com
> <javascript:>> wrote:
>
>> Hi Leandro,
>>
>> The way it is set up right now, you would actually have in the
>> Composition model a belongs_to :material. And the Material would have a
>> has_many :compositions.
>>
>> Verify that you have the foreign key set in your Composition model, so
>> you would never be able to do something like: composition.materials.
>>
>> Since you have the has_many through association you could simply call.
>> @product.materials and it will return what you want (It will do the INNER
>> JOIN through the compositions table).
>>
>> The error you're getting is because when you're using a has_and_belongs
>> to many, Rails expect to have a relationship table named after the two
>> models in the plural. But in this case your compositions table is already
>> the relationship table.
>>
>> Best regards,
>> Marco Almeida
>>
>> On Mon, Mar 30, 2015 at 3:20 PM, Leandro França <leandroay...@gmail.com
>> <javascript:>> wrote:
>>
>>> Hi there,
>>>
>>> I'm learning the active model, and I'm trying to retrieve an association.
>>>
>>> My models are:
>>>
>>> class Composition < ActiveRecord::Base
>>> has_and_belongs_to_many :materials
>>> belongs_to :product
>>> end
>>>
>>> class Material < ActiveRecord::Base
>>> has_and_belongs_to_many :compositions
>>> has_many :products, through: :composition
>>> end
>>>
>>> class Product < ActiveRecord::Base
>>> has_many :compositions
>>> has_many :materials, through: :composition
>>> accepts_nested_attributes_for :materials
>>> end
>>>
>>>
>>> My schema is:
>>>
>>>
>>> create_table "compositions", force: :cascade do |t|
>>> t.integer "product_id"
>>> t.integer "material_id"
>>> t.integer "material_quantity"
>>> t.datetime "created_at", null: false
>>> t.datetime "updated_at", null: false
>>> end
>>>
>>>
>>> create_table "materials", force: :cascade do |t|
>>> t.string "name"
>>> t.decimal "unit_cost"
>>> t.string "unit_measure"
>>> t.datetime "created_at", null: false
>>> t.datetime "updated_at", null: false
>>> end
>>>
>>>
>>> create_table "products", force: :cascade do |t|
>>> t.string "name"
>>> t.string "description"
>>> t.datetime "created_at", null: false
>>> t.datetime "updated_at", null: false
>>> end
>>>
>>> On my CompositionsController index method, I would like to retrieve all
>>> raw materials for a product id.
>>>
>>> What i have now is:
>>>
>>> def index
>>> @product = Product.find(params[:product_id])
>>> @compositions = @product.compositions
>>> end
>>>
>>>
>>> How do I retrieve materials attributes from @compositions?
>>>
>>> When I try to use
>>> @compositions = @product.compositions.includes(:materials)
>>> It gives me the error:
>>>
>>> PG::UndefinedTable: ERROR: relation "compositions_materials" does not exist
>>> LINE 5: WHERE a.attrelid = '"compositions_materials"'...
>>> ^
>>> : SELECT a.attname, format_type(a.atttypid, a.atttypmod),
>>> pg_get_expr(d.adbin, d.adrelid), a.attnotnull,
>>> a.atttypid, a.atttypmod
>>> FROM pg_attribute a LEFT JOIN pg_attrdef d
>>> ON a.attrelid = d.adrelid AND a.attnum = d.adnum
>>> WHERE a.attrelid = '"compositions_materials"'::regclass
>>> AND a.attnum > 0 AND NOT a.attisdropped
>>> ORDER BY a.attnum
>>>
>>>
>>>
>>> Any hints?
>>>
>>> Thanks in advance,
>>> Leandro
>>>
>>> --
>>> You received this message because you are subscribed to the Google
>>> Groups "Ruby on Rails: Talk" group.
>>> To unsubscribe from this group and stop receiving emails from it, send
>>> an email to rubyonrails-ta...@googlegroups.com <javascript:>.
>>> To post to this group, send email to rubyonra...@googlegroups.com
>>> <javascript:>.
>>> To view this discussion on the web visit
>>> https://groups.google.com/d/msgid/rubyonrails-talk/643eb535-3085-46d4-b77b-5c50c6cb7636%40googlegroups.com
>>>
>>> <https://groups.google.com/d/msgid/rubyonrails-talk/643eb535-3085-46d4-b77b-5c50c6cb7636%40googlegroups.com?utm_medium=email&utm_source=footer>
>>> .
>>> For more options, visit https://groups.google.com/d/optout.
>>>
>>
>>
>
--
You received this message because you are subscribed to the Google Groups "Ruby
on Rails: Talk" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to rubyonrails-talk+unsubscr...@googlegroups.com.
To post to this group, send email to rubyonrails-talk@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/rubyonrails-talk/be51416c-4340-4c12-afff-702f67820f0f%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
