Rails 4: undefined `relation_delegate_class' method for model: class

Question

I am trying to follow this coderwall guide on Creating a Limited Rail Invitation System .

In my Rails 4 application, I have the following models:

class User < ActiveRecord::Base has_many :administrations has_many :calendars, through: :administrations has_many :invitations, :class_name => "Invite", :foreign_key => 'recipient_id' has_many :sent_invites, :class_name => "Invite", :foreign_key => 'sender_id' end class Calendar < ActiveRecord::Base has_many :administrations has_many :users, through: :administrations has_many :invites end class Administration < ActiveRecord::Base belongs_to :user belongs_to :calendar end class Invite < ActiveRecord::Base belongs_to :calendar belongs_to :sender, :class_name => 'User' belongs_to :recipient, :class_name => 'User' end 

Here is the correspondence between my models and the models from the textbook:

• User <=> User
• Calendar UserGroup
• Administration Membership
• Invite Invite

Now I’m in the “Create a new invitation” section:

• The Invite model has been updated with the before_create and generate_token filters.
• Invites controller updated with create action.

However, when I look at the calendar editing view to fill out the invitation form, I get the following error:

 NoMethodError in CalendarsController#edit undefined method `relation_delegate_class' for Invite:Class def edit @user = current_user @invite = @calendar.invites.build authorize @calendar end 

The problem seems to come from the line @invite = @calendar.invites.build .

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UPDATE : here is the contents of my invitation model:

 class Invite < ActiveRecord::Base belongs_to :calendar belongs_to :sender, :class_name => 'User' belongs_to :recipient, :class_name => 'User' before_create :generate_token def generate_token self.token = Digest::SHA1.hexdigest([self.calendar_id, self.recipient_role, Time.now, rand].join) end end 

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UPDATE 2 : In this question , the author explains that the problem may come from CanCanCan and Rolify. I do not use these gems, but I use Pundit. I thought it would be useful in the context of my question.

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UPDATE 3 : the migration used for the Invite model is also used here:

 class CreateInvites < ActiveRecord::Migration def change create_table :invites do |t| t.string :email t.integer :calendar_id t.integer :sender_id t.integer :recipient_id t.string :recipient_role t.string :token t.timestamps null: false end end end 

I am wondering if the problem could be caused by t.string :recipient_role , since the role this User exists only in the Administration table for this Calendar : if :recipient_role is automatically interpreted as recipient.role Rails, maybe this causes an error?

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UPDATE 4 : here is the content of the CalendarsController:

 class CalendarsController < ApplicationController before_action :set_calendar, only: [:show, :edit, :update, :destroy] before_action :authenticate_user! # GET /calendars # GET /calendars.json def index @user = current_user @calendars = @user.calendars.all end # GET /calendars/1 # GET /calendars/1.json def show @user = current_user @calendar = @user.calendars.find(params[:id]) authorize @calendar end # GET /calendars/new def new @user = current_user @calendar = @user.calendars.new authorize @calendar end # GET /calendars/1/edit def edit @user = current_user @invite = @calendar.invites.build authorize @calendar end # POST /calendars # POST /calendars.json def create @user = current_user @calendar = @user.calendars.create(calendar_params) authorize @calendar respond_to do |format| if @calendar.save current_user.set_default_role(@calendar.id, 'Owner') format.html { redirect_to calendar_path(@calendar), notice: 'Calendar was successfully created.' } format.json { render :show, status: :created, location: @calendar } else format.html { render :new } format.json { render json: @calendar.errors, status: :unprocessable_entity } end end end # PATCH/PUT /calendars/1 # PATCH/PUT /calendars/1.json def update @user = current_user @calendar = Calendar.find(params[:id]) authorize @calendar respond_to do |format| if @calendar.update(calendar_params) format.html { redirect_to calendar_path(@calendar), notice: 'Calendar was successfully updated.' } format.json { render :show, status: :ok, location: @calendar } else format.html { render :edit } format.json { render json: @calendar.errors, status: :unprocessable_entity } end end end # DELETE /calendars/1 # DELETE /calendars/1.json def destroy @user = current_user @calendar.destroy authorize @calendar respond_to do |format| format.html { redirect_to calendars_url, notice: 'Calendar was successfully destroyed.' } format.json { head :no_content } end end private # Use callbacks to share common setup or constraints between actions. def set_calendar @calendar = Calendar.find(params[:id]) end # Never trust parameters from the scary internet, only allow the white list through. def calendar_params params.require(:calendar).permit(:name) end end 

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UPDATE 5 : here are the server logs:

 Started GET "/calendars/2/edit" for ::1 at 2015-09-14 11:44:13 -0700 Processing by CalendarsController#edit as HTML Parameters: {"id"=>"2"} Calendar Load (0.1ms) SELECT "calendars".* FROM "calendars" WHERE "calendars"."id" = ? LIMIT 1 [["id", 2]] User Load (0.2ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT 1 [["id", 1]] Completed 500 Internal Server Error in 3ms (ActiveRecord: 0.3ms) NoMethodError (undefined method `relation_delegate_class' for Invite:Class): app/controllers/calendars_controller.rb:30:in `edit' Rendered /Users/TXC/.rvm/gems/ ruby-2.2.1@global /gems/actionpack-4.2.2/lib/action_dispatch/middleware/templates/rescues/_source.erb (6.0ms) Rendered /Users/TXC/.rvm/gems/ ruby-2.2.1@global /gems/actionpack-4.2.2/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (2.8ms) Rendered /Users/TXC/.rvm/gems/ ruby-2.2.1@global /gems/actionpack-4.2.2/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (1.7ms) Rendered /Users/TXC/.rvm/gems/ ruby-2.2.1@global /gems/actionpack-4.2.2/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout (68.9ms) Rendered /Users/TXC/.rvm/gems/ruby-2.2.1/gems/web-console-2.2.1/lib/web_console/templates/_markup.html.erb (0.5ms) Rendered /Users/TXC/.rvm/gems/ruby-2.2.1/gems/web-console-2.2.1/lib/web_console/templates/_inner_console_markup.html.erb within layouts/inlined_string (0.3ms) Rendered /Users/TXC/.rvm/gems/ruby-2.2.1/gems/web-console-2.2.1/lib/web_console/templates/_prompt_box_markup.html.erb within layouts/inlined_string (0.3ms) Rendered /Users/TXC/.rvm/gems/ruby-2.2.1/gems/web-console-2.2.1/lib/web_console/templates/style.css.erb within layouts/inlined_string (0.3ms) Rendered /Users/TXC/.rvm/gems/ruby-2.2.1/gems/web-console-2.2.1/lib/web_console/templates/console.js.erb within layouts/javascript (39.3ms) Rendered /Users/TXC/.rvm/gems/ruby-2.2.1/gems/web-console-2.2.1/lib/web_console/templates/main.js.erb within layouts/javascript (0.4ms) Rendered /Users/TXC/.rvm/gems/ruby-2.2.1/gems/web-console-2.2.1/lib/web_console/templates/error_page.js.erb within layouts/javascript (0.4ms) Rendered /Users/TXC/.rvm/gems/ruby-2.2.1/gems/web-console-2.2.1/lib/web_console/templates/index.html.erb (94.2ms) 

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UPDATE 6 : I just realized that I didn’t have

 def invite_params params.require(:invite) end 

in the Invites controller: could this be causing the problem here?

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Any idea what this error message means and how to fix the problem?

Answer 1

The problem was difficult to identify, especially because of the content of the question.

PROBLEM

The reason I got the undefined method 'relation_delegate_class' for Invite:Class error is because Invite no longer considered a Rails model.

BROWN CAUSE OF THE PROBLEM

When I created the Invite mailer, I ran rails g mailer Invite instead of rails g mailer InviteMailer .

Because of this, Invite as an override of the Invite mailer as a model, therefore, generates errors as soon as methods are applied to instances of the Invite model.

HOW WE ARE STRESSED TO SEARCH

One of my friends, a more experienced programmer than me, identified the problem by changing the @invite = @calendar.invites.build that caused the error.

This led us to launch Invite.first in the rails console: while we should have either an instance of the Invite class or zero, we really got an error.

Since .first should be a valid method for any ActiveRecord model, we realized that Invite not considered a Rails model.

HOW WE EXCLUDED THIS

Once we identified the problem, the fix was pretty simple:

• We changed the name of the Invite invite.rb from invite.rb to invite_mailer.rb
• In the new renamed invite_mailer.rb file invite_mailer.rb we replaced the class Invite < ApplicationMailer with the class InviteMailer < ApplicationMailer

I hope this can be useful for other users who might get a similar relation_delegate_class error.