Simple Rails CanCanCan rule producing "association names must be a Symbol"

Question

I'm using CanCanCan for authorisation in my Rails4 project, and have a set of abilities that begins:

class Ability
  include CanCan::Ability
  def initialize(user)
    case user.role
      when :administrator
        can :manage, :all
      when :modeller
        can :manage, Model
        can :manage, Scenario
        #can :manage, MarketAssumption
# ... and so on.

In a view I have

<% if can? :view, Project %>

Which works exactly as it should. However, if I uncomment the line:

        can :manage, MarketAssumption

the view fails on the call to can? with "association names must be a Symbol".

MarketAssumption is defined in app\models\market_assumption.rb with:

class MarketAssumption < ActiveRecord::Base
  belongs_to Scenario
end

in pretty much the same way as Model and Scenario. The controller begins:

class MarketAssumptionsController < ApplicationController
  load_and_authorize_resource
  before_action :set_market_assumption, only: [:show, :edit, :update, :destroy]

as I think it should.

Where else should I look for whatever makes MarketAssumption differ from Model and Scenario in a way that CanCanCan doesn't like?

Answer 1

It's your belongs_to Scenario line. You've given that as a class name, not a symbol. Change it to belongs_to :scenario and your code should work fine. I expect that your can? call is the first time Rails tried to load a MarketAssumption object in your app, so that's the first time that error occurs.

You can find out more about setting up associations in the Rails guides.