has_many with model name as foreign key

rubyonrails-talk
1

Hi,

It’s possible to do this :

models:

  • product has_many attributes
  • user has_many attributes
  • other_model has_many attributes

model attribute belongs to

  • product , but the foreign_key is not product_id but the mode name (Product) stored in table attributes(id, name, model)
  • user , but the foreign_key is not product_id but the mode name (Product) stored in table attributes(id, name, model) I want associate the attributes model with whole model and not with single record.

thx

2

Hi,

Fistly, dont create a model with the name “Attribute”. Some of the rails core methods uses “attributes” . Use something like “custom_attributes” .

Next, to make a model belong_to different models on the same foreign_key, Make sure you use polymorphic-associations in rails.

3

thx,

but with polymorphic associations, i always need to set a foreign key column,

my need is to set only the column type (model name)…

class Picture < ActiveRecord::Base belongs_to :imageable, polymorphic: true

#table pictures (id, name, imageable_id, imageable_type)

how use it without imageable_id

end

class Employee < ActiveRecord::Base has_many :pictures, as: :imageable end

class Product < ActiveRecord::Base has_many :pictures, as: :imageable end

``

4

Explain the problem that you are trying to solve with this unusual scheme. It may well be that there is a better way of solving it.

Colin

5

i have many model that user want add or remove attribute dynamically

example :

table / model : product (id, name, price, metadata (serialized column , hash) ) table /mode : other_model (id, name, xxx_attribute, , metadata (serialized column , hash) )

table / model : my_custom_fields (id, name , field_type , model (column contain model name) )

form and fields view are generate dynamically (with partial)

i can do it by :

class product < AR::Base serialize :metadata , Hash

#i save all my custom attributes in metadata column

def get_all_custom_attributes My_custom_field.find_by_model(self.class.name) end

end

``

but i need a properly way if there is one :wink: