gistfile1.rb

#publications_controller

def show
    @comments = @publication.comments.includes(:author => :user).order('created_at desc').page(params[:page]).per(10) 
    @comment = @publication.comments.build
  end

#comments_controller
def create                
    @publication = Publication.find(params[:publication_id])
    @comment = @publication.comments.new(params[:comment])  
    @comment.author = current_user.accountable    
    authorize! :create, @comment
    if @comment.save
      redirect_to institute_publication_url(current_institute, @publication), :notice => "Successfully created comment."
    else                               
      @comments = @publication.comments.includes(:author => :user).order('created_at desc').page(params[:page]).per(10) 
      render :template => "publications/show"
    end
  end