Question

I have a Type has_many Dresses. In the Dress table, I have a column called type_id which references the Type model. What I want to do is whenever a Type object is deleted, all of the associated Dress objects will update their type_id to nil.

So far, I tried this in the console and it works:

> Dress.where(type_id: 3).update_all(type_id: nil)

However, when I translate it in the TypesController like this:

def destroy
  type_id = params[:id]
  if Type.find(type_id).destroy
    Dress.where(:type_id => type_id).update_all(:type_id => nil)
    redirect_to admins_path
  end
end

…and try it in the browser, the Type object is deleted but the Dress type_id was not updated.

This is the log output:

DELETE FROM "types" WHERE "types"."id" = $1  [["id", 3]]
UPDATE "types" SET position = (position - 1) WHERE (1 = 1 AND position > 2)
COMMIT
UPDATE "dresses" SET "type_id" = NULL WHERE "dresses"."id"
  IN (SELECT "dresses"."id" FROM "dresses" WHERE "dresses"."type_id" = 0)

I don’t understand why it sets the type_id = 0 in the last UPDATE command but before that it was set correctly in the DELETE command.

Answer 1

class Type < ActiveRecord::Base
    has_many :dresses, :dependent => :nullify
    ...
end

Does not it work?