refactored controller with topics_params method

topics_controller.rb

def create
    @topic = Topic.new(topics_params)
    authorize @topic
    if @topic.save
      redirect_to @topic, notice: "Topic was saved successfully."
    else
      flash[:error] = "Error creating topic. Please try again."
      render :new
    end
  end

  def update
    @topic = Topic.find(params[:id])
    authorize @topic
    if @topic.update_attributes(topics_params)
      redirect_to @topic
    else
      flash[:error] = "Error updating topic. Please try again."
      render :edit
    end
  end

  private

  def topics_params
    params.require(:topic).permit(:name, :description, :public)
  end

end