CODEWITHSUNDEEP
ruby-on-railsrubyruby-on-rails-4
bootsa
bootsa

Reputation: 249

Has_many rails association => NoMethodError

If I have three classes in rails:

class Item::Part::Element < ActiveRecord::Base
  belongs_to :item_part, :foreign_key => 'item_part_id'
  self.table_name = 'item_part_elements'
end


class Item::Part < ActiveRecord::Base
  has_many :elements
  belongs_to :item, :foreign_key => 'item_id'
  self.table_name = 'item_parts'
end

class Item < ActiveRecord::Base
 has_many :parts
 self.table_name = 'item'
end

and if I call 

@item.parts

it works fine, but if I make following call

@item_part.elements

throws an error 

NoMethodError: undefined method "elements"

Have I done my associations wrong or is there a different issue?

Upvotes: 0

Views: 485

Answers (1)

Jaime Bellmyer
Jaime Bellmyer

Reputation: 23317

I believe you need to specify class names for these associations. If you didn't have namespacing, these would work fine out of the box. But since you have Item::Part::Element instead of simply Element, you have to give ActiveRecord more to go on. Try this:

class Item::Part::Element < ActiveRecord::Base
  belongs_to :item_part, :foreign_key => 'item_part_id'
  self.table_name = 'item_part_elements'
end


class Item::Part < ActiveRecord::Base
  has_many :elements, :class_name => '::Item::Part::Element'
  belongs_to :item, :foreign_key => 'item_id'
  self.table_name = 'item_parts'
end

class Item < ActiveRecord::Base
 has_many :parts, :class_name => '::Item::Part'
 self.table_name = 'item'
end

The reason the class_names start with "::" is that it tells ActiveRecord you're namespacing from the top (root) of the namespace structure, instead of relative to the current model.

Honestly, I have a little trouble believing that @item.parts works properly!

Upvotes: 1

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