Ruby on Rails Sunday, September 20, 2015



On Saturday, 19 September 2015 12:03:47 UTC-4, Oto Iashvili wrote:

Hi,

I have a product class with category and  a polymorphic attributes details_info, that depending on category go to one or another table to get the detail


Class Product
category
details_info

end

Class DetailsInfo
...
end

Class Pencil

  include DetailsInfo
type
color
end

Class Notebook

  include DetailsInfo
size
...
end

and to display products i do
prds = Products.all
prds.each do |pr|

if pr.category == 'pencil'
DetailsInfo.table_name = 'pencil'

else if pr.category == 'notebook'

DetailsInfo.table_name = 'notebook'
end

end

(this is just kind of algo I use)

All this was working fine but with rails > 4.2 , it doesnt work anymore.
The first time pr.details_info will be called, it seems that the table name is cached somewhere, and then all other products are using the same table_name. When I check during loop, I can see that DetailsInfo.table_name is always correct, but still when pr.details_info will be called , it used the first table_name that was used. I can also see that the method table_name is called every step of the loop, and it return the good table_name, but still, the sql request search on bad table.

How can I reset that ? Ive tried a lot a thing like emptying association_cache, also different things with reflect_on_all_associations, reset_column_information, reload, ...


As mentioned on rails-core, I'd recommend looking into polymorphic associations for this. Here's a possible example:
```
  class Product < ActiveRecord::Base
    # the products table has two columns relevant here:
    #   * details_info_id, integer
    #   * details_info_type, string
    belongs_to :details_info, polymorphic: true
  end

  class Pencil < ActiveRecord::Base
    has_many :products, as: :details_info
  end

  class Notebook < ActiveRecord::Base
    has_many :products, as: :details_info
  end
```

Given those models, if you retrieve a list of Product objects you should be able to access each one's `details_info` from the correct tables.

If you're still unsure how to proceed, more detail on the specifics of your schema and desired functionality would be useful.

--Matt Jones

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