Before_save = Change default value for many to many

问题

Can someone help me figure out what code I should put in my change_default method?

I would like to be able to do something like this...

user = User.find(1)
user.companies.first.default!
or 
user.companies.find_by_company_id(2).default!

My code:

class Role < ActiveRecord::Base 
  before_save :change_default

  belongs_to :user
  belongs_to :company

  def change_default
    #update default field for to false for current scope
    #Update current record default field to true

    #this is what I currently have, but it's not setting my defaults to false
    if self.default == true
     roles = Roles.where( :user_id => self.user_id) 
     roles.update_all(:default => false)
    end
  end

  def default!
    self.default=true
    self.save
  end

end

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

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

Code run:

pry(main)> a.roles.last.default!

   (0.1ms)  begin transaction
SCOPING
  SQL (0.4ms)  UPDATE "roles" SET "default" = 'f' WHERE "roles"."user_id" = 1
   (2.0ms)  commit transaction
=> true

[5] pry(main)> a.roles

=> [#<Role id: 1, company_id: 1, name: nil, view_document: nil, edit_document: nil, upload_document: nil, delete_document: nil, review_document: nil, company_info: nil, company_clients: nil, company_users: nil, company_admin: nil, created_at: "2014-08-04 20:10:23", updated_at: "2014-08-04 22:29:40", user_id: 1, default: true>,

    #<Role id: 2, company_id: 2, name: nil, view_document: nil, edit_document: nil, upload_document: nil, delete_document: nil, review_document: nil, company_info: nil, company_clients: nil, company_users: nil, company_admin: nil, created_at: "2014-08-04 20:11:10", updated_at: "2014-08-04 20:11:10", user_id: 1, default: nil>,

    #<Role id: 3, company_id: 3, name: nil, view_document: nil, edit_document: nil, upload_document: nil, delete_document: nil, review_document: nil, company_info: nil, company_clients: nil, company_users: nil, company_admin: nil, created_at: "2014-08-04 20:11:14", updated_at: "2014-08-04 22:29:16", user_id: 1, default: true>]

As you can see the update ran, but the default values are not set to false. If you have any recommendations or things I can check, please let me know.

回答1:

Needed to exclude the current record that is being modified. Added the where.not clause

  def change_default
    if self.default_changed? && self.default == true
      roles = Role.where( :user_id => self.user_id)
      roles = roles.where.not(:id => self.id)
      roles.update_all(:default => false)  
    end
  end

回答2:

Looks like in the example you never call save on the roles. Therefore, your before_save :change_default is not being executed. Perhaps adding role.save in def default! would at least have the before_save be executed because I'm not sure that your current console test is actually running the change_default method.

If I am wrong and it actually is running, then I'm not sure why your block would not set the default value to false.

来源：https://stackoverflow.com/questions/25127986/before-save-change-default-value-for-many-to-many

标签

ruby-on-rails-4

many-to-many

before-save