def new
    authorize! :create, FundRemitBulk
    @allocation_type = params[:allocation_type]
    @fund_remit_bulk = FundRemitBulk.new
    default_customer_corporate_bank =
      CustomerCorporateBank.find(:first,:conditions => {:default_payment => 1})
    @fund_remit_bulk.customer_corporate_bank_id = 
      default_customer_corporate_bank.try(:id)
    @fund_remit_bulk.account_bank = 
      default_customer_corporate_bank.try(:account_bank)
    @fund_remit_bulk.account_number =
      default_customer_corporate_bank.try(:account_number)
    if @allocation_type == "asset_securitization"
      fund_allocations = FundAllocation.abs_allocations
    else
      fund_allocations = FundAllocation.fund_outflow_allocations
    end
    @fund_allocations = fund_allocations.where(:allocated => false)
    respond_to do |format|
      format.html # new.html.erb
      format.xml  { render :xml => @fund_remit_bulk }
    end
  end

上述代码是 FundRemitBulk 的 new，项目中多个模块中都有 new_fund_remit_bulk 的入口，是以 allocation_type 来区分的，即 fund_remit_bulks/new?allocation_type=**; fund_remit_bulk.rb 中对多个字段进行 validates_presence_of 处理，save 失败后，会在相应位置显示非空错误信息（只是需要保证的效果）

下面是 create 的异常捕获

rescue Exception => e
   msg = "新建资金调拨单出错：#{e.message}"
   @fund_remit_bulk.errors.add(:base,msg)
   raise ActiveRecord::Rollback, msg
 end

e.message 显示的是“数据校验未通过”,显然不是我想要的

format.html { redirect_to(new_fund_remit_bulk_path(:allocation_type => type),
                                  :alert => @fund_remit_bulk.errors[:base].join("\n")) }

redirect_to 可以保证 create 失败后停留在正确的新建页面，但是却不能显示非空错误信息，用 render :action => "new"可以实现，但是需要指定 allocation_type。 能否用 render？该如何传参？网上查了不少，但是没看到有谁这么用