CanCan plugin

Posted on 2010-11-25
Last Modified: 2012-05-10

  I am using the Can Can plugin and if you are familiar with it perhaps you can help me.
  I need to create this class Ability. The Ability class has the initialize method and I'd like to add a new parameter there.
  This parameters doesn't come and perhaps somebody could help me.
  Here is the plugin:

class Ability
  include CanCan::Ability

  def initialize(user, user_role)
    case (user_role)
      when 1: # administrator
        can :manage, :all
      when 2: # presbyter
        can :read, :all
      when 3: # secretary
        can :read, :all
      when 4: # area_pastor
        can :read, :all
      when 5: # coordinator
        can :read, :all
      when 6: # supervisor
        can :read, :all
      when 7: # leader
        can :read, :all
      when 8: # member
        can :read, :all
      when 9: # frequenter
        can :read, :all      
        # guest user, what TODO ??

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and I am calling like this:
        <% if can? :update, ConfigMaster, current_user_role %>
       <% end %>

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Question by:lusfernandos
  • 4
  • 3
LVL 12

Accepted Solution

JESii earned 500 total points
ID: 34215427
You may be able to override the definition of initialize as you did, but that's only half the problem. You also have to find where the Ability class instance is created (with the expression) and change those as well.

For example, in lines 276-278 of the file cancan/lib/cancan/controller_additions.rb a new Ability instance is created and there is only one parameter there.

You may be able to solve this problem by leaving only a single parameter but attaching your roles to the user instance, so that you can reference user.user_role
#Code from lines 276-278 of cancan/lib/cancan/controller_additions.rb
    def current_ability
      @current_ability ||=

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Author Comment

ID: 34217156
Hi JESii,

  Thanks for your answer. I thought I could do something without changing the plugin/gem. Thinking this way your second suggestion would be perfect, however I did tried sometime back adding an attribute to User, but I wasn't able to ( I am new to Rails ...).
  I am using the authlogic for authenticating the user, so I need to know the exact place to add this attribute. I am thinking about
1) Add a new virtual attribute to User class
2) When the user log in I need to update  that information.
  def current_user
    return @current_user if defined?(@current_user)
    @current_user = current_user_session && current_user_session.record

  Can you point me to the right direction? Thanks a lot

Author Comment

ID: 34217367
Just to add more information about what I am trying to accomplish.
First my login screen has the fields: user, password and role. This means that a user can have several role, however it will login as a specific role.
The role that the user is logged in needs to be checked in the CanCan and now I need to have it saved somehow to my User Model.
This role is just related to the current session, so I believe I just need to add a virtual attribute, I don't actually need to save this info to the database (right?)
Currently I am storing the current_user_role in the session ...
  def current_user_role=(user_role)
    logger.debug "current_user_role (set) --> = #{user_role}"
    session[:user_role] = user_role
    @current_user_role = user_role
    logger.debug "current_user_role (set) #{session[:user_role]}<--"

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Hopefully now it is more clear ...
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LVL 12

Expert Comment

ID: 34217951
I don't have a specific answer off the top of my head, but here are some thoughts that might be of help to you.

I've used AuthLogic, but always had problems extending it or getting it to play nice with other things I needed to do. I'm going to try Devise on my next project as I hear it's easier to work with:

For AuthLogic & CanCan, I've found the following which might help.

1.  - has combined AuthLogic, CanCan, and EasyRoles into a single engine that you can install that seems to have everything you need

2. - Is a gem to do authentication and authorization

3. - has a basic Rails application template that includes AuthLogic, CanCan and other basic components

Author Closing Comment

ID: 34232574
I was able to add the user_role to the Users model.
LVL 12

Expert Comment

ID: 34232911
Good, lusfernandos... glad that worked out; that's pretty much the standard way to handle a situation like this. And thanks for the points!

Author Comment

ID: 34232956
Thanks, Hope that you help me next time as well :)

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