Rails查询结果判断

def search
          title = params[:product][:keyword]
         author_name = params[:product][:author_name]
         @products = Product.find(:all, :conditions => [ "title LIKE ? and author_name LIKE ? "  , "%#{title}%", "%#{author_name}%" ] )

         respond_to do |format|
        if @products == nil  || @products == ""#验证product对象不为空
          flash[:notice] ="can not find the product!"
         format.html{redirect_to(products_url)}
         format.xml  { render :xml => @products }
      else  if title == nil || title == ""  #验证表单不为空
         flash[:notice] = "keyword can not be blank !"
        format.html{redirect_to(products_url)}
        format.xml  { render :xml => @products }
   
   else
      if @products == nil
       flash[:notice] == "can not find!"
      else
        flash[:notice] = "find the product for you!"
        format.html#{ redirect_to(search_products_url(@products)) }
        format.xml  { render :xml => @products }
   end
   end
    end
  end
  end

但是一直都执行不了  if @products == nil  || @products == ""#验证product对象不为空
以及 else
      if @products == nil

其实:all的时候返回的是一个数组 数组为空 可以用@products.empty? 来判断

或者用@products.length > 0来判断

如果是一个对象 也就是object 可以用@products.nil?来判断

而且

find_by_id#没有返回就会出错