Possible to alias a belongs_to association in Rails?
Solution 1:
No it doesn't look for company_id for instance change your code as follows
In Rails3
class Car < ActiveRecord::Base
belongs_to :vendor
belongs_to :company, :class_name => :Vendor,:foreign_key => "vendor_id"
end
In Rails4
We can use alias attribute.
alias_attribute :company, :vendor
Solution 2:
In Rails 4, you should simply be able to add alias_attribute :company, :vendor
to your model.
Solution 3:
Short Version:
-
Generate model with migration
$ rails generate model Car vendor:references name:string ...
-
Add following line in
Car
model i.ecar.rb
fileclass Car < ActiveRecord::Base belongs_to :company, :class_name => 'Vendor', :foreign_key => 'vendor_id' end
Now you have
@car.company
instance method.
For a Detailed explanation read ahead [Optional if you understood the above !!]
Detailed Version:
The model Car
will have an association with the model Vendor
(which is obvious). So there should be a vendor_id
in the table cars
.
-
In order to make sure that the field
vendor_id
is present in thecars
table run the following on the command line. This will generate the right migration. Thevendor:references
is important. You can have any number of attributes after that.$ rails generate model Car vendor:references name:string
-
Or else in the existing migration for
create_table :cars
just add the linet.references :vendor
class CreateCars < ActiveRecord::Migration def change create_table :cars do |t| t.string :name ... t.references :vendor t.timestamps end end end
-
The final thing that you need to do is edit the model
Car
. So add this code to yourcar.rb
fileclass Car < ActiveRecord::Base belongs_to :company, :class_name => 'Vendor', :foreign_key => 'vendor_id' end
After you do the third step you will get the following instance methods for the model Car
provided by Rails Associations
-
@car.company
When you do
@car.company
it will return a#<Vendor ...>
object. To find that#<Vendor ...>
object it will go look for thevendor_id
column in thecars
table because you have mentioned:foreign_key => 'vendor_id'
-
You can set the company for a car instance by writing
@car.company = @vendor || Vendor.find(params[:id]) #whichever Vendor object you want @car.save
This will save the
id
of thatVendor
object in thevendor_id
field of thecars
table.
Thank You.
Solution 4:
class Car < ActiveRecord::Base
belongs_to :vendor
belongs_to :company, :class_name => :Vendor
end