Action Aliases

You will usually be working with four actions when defining and checking permissions: :read, :create, :update, :destroy. These aren't the same as the 7 RESTful actions in Rails. CanCan automatically adds some convenient aliases for mapping the controller actions.

alias_action :index, :show, :to => :read
alias_action :new, :to => :create
alias_action :edit, :to => :update

Notice the edit action is aliased to update. This means if the user is able to update a record he also has permission to edit it. You can define your own aliases in the Ability class.

class Ability
  include CanCan::Ability
  def initialize(user)
    alias_action :update, :destroy, :to => :modify
    can :modify, Comment
  end
end

# in controller or view
can? :update, Comment # => true

You are not restricted to just the 7 RESTful actions, you can use any action name. See Custom Actions for details.

Please note that if you are changing the default alias_actions, the original actions associated with the alias will NOT be removed. For example, following statement will not have any change on the alias :read, which points to :show and :index:

alias_action :show, :to => :read #this will have no change on the alias :read!

If you want to change the default actions, you should use clear_aliased_actions method to remove ALL default aliases first.