<% if can? :update, @article %>
    <%= link_to "Edit", edit_article_path(@article) %>
  <% end %>

user.can?(:update, @article)

class User < ActiveRecord::Base
  def ability
    @ability ||= Ability.new(self)
  end
  delegate :can?, :cannot?, :to => :ability
end

user.can?(:update,@article)