Mongoid::Errors::AmbiguousRelationship in Users#show

Question

I use ruby '2.5.0', rails, '5.2.2', mongoid '7.0.2' and devise

I try to add follow function, but I have this error in mongoid '7.0.2'

message: Ambiguous relations

@options={:class_name=>"User"}, @extension=nil, @module_path="", @polymorphic=false, @default_foreign_key_field="follower_id", @foreign_key="follower_id", @indexed=false, @class_name="User", @klass=User, @validate=false>,

@options={:class_name=>"User"}, @extension=nil, @module_path="", @polymorphic=false, @default_foreign_key_field="followed_id", @foreign_key="followed_id", @indexed=false, @class_name="User", @klass=User, @validate=false> defined on Relationship. summary: When Mongoid attempts to set an inverse document of a relation in memory, it needs to know which relation it belongs to. When setting :relationships, Mongoid looked on the class User for a matching relation, but multiples were found that could potentially match:

@options={:class_name=>"User"}, @extension=nil, @module_path="", @polymorphic=false, @default_foreign_key_field="follower_id", @foreign_key="follower_id", @indexed=false, @class_name="User", @klass=User, @validate=false>,

@options={:class_name=>"User"}, @extension=nil, @module_path="", @polymorphic=false, @default_foreign_key_field="followed_id", @foreign_key="followed_id", @indexed=false, @class_name="User", @klass=User, @validate=false>. resolution: On the :relationships relation on User you must add an :inverse_of option to specify the exact relationship on Relationship that is the opposite of :relationships.

user.rb

class User
  include Mongoid::Document

  field :email, type: String, default: ""

  has_many :relationships, foreign_key: "follower_id", dependent: :destroy
  has_many :reverse_relationships, foreign_key: "followed_id", class_name: "Relationship", dependent: :destroy

  def retrieve_users_for_ids(user_ids)
    users = []
    User.in(id: user_ids).each do |user|
      users << user
    end

    users
  end

  def followed_users
    user_ids = []
    relationships.each do |relationship|
      user_ids << relationship.followed_id
    end

    return retrieve_users_for_ids(user_ids)
  end

  def followers
    user_ids = []
    reverse_relationships.each do |relationship|
      user_ids << relationship.follower_id
    end

    return retrieve_users_for_ids(user_ids)
  end

  def following?(other_user)
    relationships.where(followed_id: other_user.id).first
  end

  def follow!(other_user)
    relationships.create!(followed_id: other_user.id)
  end

  def unfollow!(other_user)
    relationships.where(followed_id: other_user.id).first.destroy
  end
end

_follow.html.erb

<%= form_for(current_user.relationships.build(followed_id: @user.id),
             remote: true) do |f| %>
  <%= f.hidden_field :followed_id %>
  <%= f.submit 'Follow', data: {disable_with: 'Follow...'}, class: 'btn btn-d' %>
<% end %>

Anton Ipatov Anton Ipatov · Accepted Answer · 2019-01-22T09:25:40

Found a working solution

user.rb

class User
  include Mongoid::Document

  has_and_belongs_to_many :following, class_name: 'User', inverse_of: :followers
  has_and_belongs_to_many :followers, class_name: 'User', inverse_of: :following

  def follow(other_user)
    self.following << other_user
    other_user.followers << self
  end

  def unfollow(other_user)
    self.following.delete(other_user)
    other_user.followers.delete(self)
  end

  def following?(other_user)
    self.following.include?(other_user)
  end
end

users_controller.rb

class UsersController < ApplicationController
  def following
    @title = 'Following'
    @user = User.find(params[:id])
    @users = @user.following.page(params[:page])
    render 'show_follow'
  end

  def followers
    @title = 'Followers'
    @user = User.find(params[:id])
    @users = @user.followers.page(params[:page])
    render 'show_follow'
  end
end

relationships_controller.rb

class RelationshipsController < ApplicationController
  def create
    @user = User.find(params[:user_id])
    current_user.follow(@user)
    respond_to do |format|
      format.html { redirect_to @user }
      format.js
    end
  end

  def destroy
    @user = User.find(params[:user_id])
    current_user.unfollow(@user)
    respond_to do |format|
      format.html { redirect_to @user }
      format.js
    end
  end
end

routes.rb

Rails.application.routes.draw do
  resources :users do
    member do
      get :following, :followers
    end
  end

  post   '/follow/',  to: 'relationships#create'
  delete '/unfollow', to: 'relationships#destroy'
end

views/relationships/create.js.erb

$("#follow_form").html("<%= escape_javascript(render('users/unfollow')) %>")
$("#followers").html('<%= @user.followers.count %>')

views/relationships/destroy.js.erb

$("#follow_form").html("<%= escape_javascript(render('users/follow')) %>")
$("#followers").html('<%= @user.followers.count %>')

views/users/_follow_form.html.erb

<% unless current_user?(@user) %>
  <div id="follow_form">
  <% if current_user.following?(@user) %>
    <%= render 'unfollow' %>
  <% else %>
    <%= render 'follow' %>
  <% end %>
  </div>
<% end %>

views/users/_follow.html.erb

<%= form_tag "/follow", method: :post , remote: true do %>
  <%= hidden_field_tag :user_id, @user.id %>
  <%= submit_tag "Follow", data: {disable_with: 'Follow...'}, class: "btn btn-d" %>
<% end %>

views/users/_unfollow.html.erb

<%= form_tag "/unfollow", method: :delete , remote: true do %>
  <div><%= hidden_field_tag :user_id, @user.id %></div>
  <%= submit_tag "Unfollow", data: {disable_with: 'Unfollow...'}, class: "btn btn-d" %>
<% end %>

views/users/show.html.erb

<% if current_user == @user %>
  <%= render 'follow_form' %>
<% end %>

Mongoid::Errors::AmbiguousRelationship in Users#show

1 Answers