Rails 4-如果不使用'has_one'关联创建新的嵌套模型，则无法保存模型

Question

I have a Visibility model, which has some boolean attributes and other things defining how other models can be seen. Visibility is polymorphic, because I want it to belong to both the User and Activity models. Visibility:

class Visibility < ActiveRecord::Base  
  belongs_to :viewable, :polymorphic => true
end

User (edited to include totality):

class User < ActiveRecord::Base
  # Relations
  #has_many :posts
  has_one :fb_connection
  has_many :activities
  has_many :participations
  has_many :activities, :through => :participations
  has_one :visibility, as: :viewable, dependent: :destroy
  accepts_nested_attributes_for :visibility

  has_many :friendships
  has_many :friends, :through => :friendships
  has_many :sent_friend_invites, :through => :friendships
  has_many :received_friend_invites, :through => :friendships

  devise :database_authenticatable, :registerable,
  :recoverable, :rememberable, :trackable, :validatable, :confirmable

  # Callback to set a user's default visibility for their activities
  before_save :default_values

  # paperclip helper method
  has_attached_file :profile_pic, styles: {
    thumb: '100x100>',
    square: '200x200#',
    medium: '300x300>'
  }, default_url: "https://dl.dropboxusercontent.com/u/743320/q_silhouette.gif"


  # Pagination
  paginates_per 100

  # Validations
  # :email
  validates :first_name, presence: true
  validates :last_name, presence: true
  validates_format_of :email, with: /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i

  # Paperclip validation
  validates_attachment :profile_pic, :size => { :in => 0..10.megabytes }, :content_type => { :content_type => /^image\/(jpeg|png|gif|tiff)$/}

  def self.paged(page_number)
    order(admin: :desc, email: :asc).page page_number
  end

  def self.search_and_order(search, page_number)
    if search
      where("email LIKE ?", "%#{search.downcase}%").order(
      admin: :desc, email: :asc
      ).page page_number
    else
      order(admin: :desc, email: :asc).page page_number
    end
  end

  def self.last_signups(count)
    order(created_at: :desc).limit(count).select("id","email","created_at")
  end

  def self.last_signins(count)
    order(last_sign_in_at:
    :desc).limit(count).select("id","email","last_sign_in_at")
  end

  def self.users_count
    where("admin = ? AND locked = ?",false,false).count
  end

  def get_display_name
    if display_name =~ /./  # Just check that the display name is not ""
      #puts "display name: " + display_name
      return display_name
    else
      #puts "name: " +  [first_name, last_name].join(" ")
      return [first_name, last_name].join(" ")
    end
  end

  def get_profile_pic_thumb
    return profile_pic(:thumb)
  end

  def measurement_labels
    return I18n.t('user_label_use_metric_true') if use_metric      
  end

  private

  def default_values
    viewable ||= Visibility.create(default_viewable_params)  
  end

  def default_viewable_params
    {:public => true, :app_friends => true, :facebook_friends => true, :strava_friends => true, :viewable => self }
  end
end

Activity (relevant parts):

class Activity < ActiveRecord::Base
    ...  
    has_one :visibility, as: :viewable, dependent: :destroy
    ...
end

I can't for the life of me get this to work. Any time I just save a user model -- even if the Visibility model is not modified -- it creates a NEW Visibility model for the user. Eg, in the console:

user = User.find(5)
user.foo = false
user.save

I get this output:

(0.4ms) BEGIN SQL (1.0ms) INSERT INTO "visibilities" ("public", "app_friends", "facebook_friends", "viewable_id", "viewable_type", "created_at", "updated_at") VALUES ($1, $2, $3, $4, $5, $6, $7) RETURNING "id" [["public", "t"], ["app_friends", "t"], ["facebook_friends", "t"], ["viewable_id", 5], ["viewable_type", "User"], ["created_at", "2015-10-23 23:06:57.431922"], ["updated_at", "2015-10-23 23:06:57.431922"]] (21.3ms) COMMIT => true

And naturally, trying to update the Visibility model through User fails. While it is updated, a new one is also created in its place. Here is the applicable user_controller methods and view using simple_form_for:

#user_controller
def preferences
    @user = current_user
    if !@user.visibility
      @user.visibility = Visibility.new
    end   
end

def update_preferences
    user = current_user
    user.update!(user_pref_params)
    flash[:notice] = I18n.t('user_flash_update_success')
    redirect_to profile_path(user)    
end

private 

def user_pref_params
    params.require(:user).permit(:use_metric, visibility_attributes: [:id, :public, :app_friends, :facebook_friends])
end

---

<!-- preferences form -->
<%= simple_form_for @user, :url => update_preferences_path do |f| %>            
    <%= f.simple_fields_for :visibility do |v| %>
        <%= v.input :public, label: t('user_preferences_label_public'), as: :select, required: false %>
        <%= v.input :app_friends, label: t('user_preferences_label_app_friends'), as: :select, required: false %>
        <%= v.input :facebook_friends, label: t('user_preferences_label_facebook_friends'), as: :select, required: false %>     
    <% end %>
    <!-- Preference for system of measurement -->
    <%= f.input :use_metric, as: :select, collection: [[t('user_preferences_use_metric_true'), true], [t('user_preferences_use_metric_false'), false]], label: t('user_preferences_label_use_metric'),  include_blank: false %> 

    <!-- Submit button -->
    <%= f.button :submit, :label => "Save", :class => "btn btn-primary" %>
<% end %>

This attempt at mass assignment gives me this feedback:

Started PATCH "/users/updateprefs" for 127.0.0.1 at 2015-10-23 17:02:52 -0700 Processing by UsersController#update_preferences as HTML Parameters: {"utf8"=>"✓", "authenticity_token"=>"FXj3kWxNDE7tl7InvBvL68UzlvmWR/d3aJ4/gTg7cCCEGEafJJZO10ud31kU2120SdKF3aNj5gy0FiizURHTeQ==", "user"=>{"visibility_attributes"=>{"public"=>"false", "app_friends"=>"false", "facebook_friends"=>"false", "id"=>"64"}, "use_metric"=>"true"}, "commit"=>"Update User"} User Load (0.4ms) SELECT "users".* FROM "users" WHERE "users"."id" = $1 ORDER BY "users"."id" ASC LIMIT 1 [["id", 55]] (0.3ms) BEGIN Visibility Load (0.8ms) SELECT "visibilities".* FROM "visibilities" WHERE "visibilities"."viewable_id" = $1 AND "visibilities"."viewable_type" = $2 LIMIT 1 [["viewable_id", 55], ["viewable_type", "User"]] SQL (0.6ms) INSERT INTO "visibilities" ("public", "app_friends", "facebook_friends", "viewable_id", "viewable_type", "created_at", "updated_at") VALUES ($1, $2, $3, $4, $5, $6, $7) RETURNING "id" [["public", "t"], ["a pp_friends", "t"], ["facebook_friends", "t"], ["viewable_id", 55], ["viewable_type", "User"], ["created_at", "2015-10-24 00:02:52.244397"], ["updated_at", "2015-10-24 00:02:52.244397"]] SQL (0.5ms) UPDATE "users" SET "use_metric" = $1, "updated_at" = $2 WHERE "users"."id" = $3 [["use_metric", "t"], ["updated_at", "2015-10-24 00:02:52.247304"], ["id", 55]] SQL (0.5ms) UPDATE "visibilities" SET "app_friends" = $1, "updated_at" = $2 WHERE "visibilities"."id" = $3 [["app_friends", "f"], ["updated_at", "2015-10-24 00:02:52.250120"], ["id", 64]] (13.3ms) COMMIT

As you can see, Rails is both creating a new visibility and updating the existing one! I can maybe jerry-rig this to work around it with some really ugly code, but I would appreciate any help to keep my controller actions clean.

Answer 1

In your User model, in the default_values method, you're creating a new visibility and assigning it to viewable . However, this is scoped such that it is only available to the method, not the class as a whole (and thus does comparison against the method variable).

Also, viewable is the correct usage of the association only in the Visibility model. In the User model, you will have to reference it as visibility .

What needs to be done is to use self to apply the comparison and assignment to the instance variable instead.

def default_values
  self.visibility ||= Visibility.create(default_viewable_params)  
end