Is there a way to stop this default insert in rails

问题

Ok so i have this data structure

class User < ActiveRecord::Base
  has_many :companies, :through => :positions
  has_many :positions

class Company < ActiveRecord::Base
  has_many :positions
  has_many :users, :through => :positions

class Position < ActiveRecord::Base
  belongs_to :company
  belongs_to :user
  attr_accessible :company_id, :user_id, :regular_user
end

And my database structure

create_table "positions", :force => true do |t|
  t.integer  "company_id"
  t.integer  "user_id"
  t.datetime "created_at",                     :null => false
  t.datetime "updated_at",                     :null => false
  t.boolean  "regular_user", :default => true
end

And if i add another company to a users companies, the regular_user flag is always set to true

1.9.3-p125 :013 > @user.companies << Company.last
  Company Load (0.3ms)  SELECT `companies`.* FROM `companies` 
  ORDER BY `companies`.`id` DESC LIMIT 1
   (0.0ms)  BEGIN
  SQL (0.2ms)  INSERT INTO `positions` 
(`company_id`, `created_at`, `regular_user`, `updated_at`, `user_id`) 
VALUES 
(263, '2012-07-25 13:56:56', 1, '2012-07-25 13:56:56', 757)

Is there a way to set the flag to false before the insert

I have been getting around it by doing this....which is hackish

@user.positions.update_all(:regular_user => false) if @user.is_admin?

Is there another way (cleaner) to achieve this

回答1:

Use a before_save filter.
Ex.:

class Position

  before_save :set_regular_user_to_false

  def set_regular_user_to_false
    self.regular_user = false
  end

end

Like the filter name says, this will intercept the chain of events right before saving the position object, so you can change the regular_user attribute.

EDIT

def set_regular_user_to_false
  if self.user.user_type != 'admin'
    self.regular_user = false
  end
  true
end

回答2:

You can directly insert a position

user.positions << Position.new(company: Company.last, regular_user: false)

回答3:

Honestly its been a while since I've used AR migrations so double check my syntax before you run this on a production database.

Having said that, this is being set on a database level as your table structure has that set to true. So if a NULL situation exists it will be made true.

You should be able to run a migration that will change your database column to default to false. You can also override with a callback as @MurifoX suggests, but I think this better addresses your core complaint.

Good Luck!

class ChangePostitionsRegularUser < ActiveRecord::Migration

  def up
    change_column :positions, :regular_user, :boolean, :default => false
  end

  def down
    change_column :positions, :regular_user, :boolean, :default => true
  end
end

来源：https://stackoverflow.com/questions/11651489/is-there-a-way-to-stop-this-default-insert-in-rails