Ruby on rails 调用ruby方法也可以导出csv

我有以下代码：

def first
  @distribution_sheet = DistributionSheet.find(:all, :conditions => ["lifecycle_state = ?","closed"]).last
  @results = @distribution_sheet.results
  @specimens = @distribution_sheet.specimens
end

include DisplayResultHelper
def show
  respond_to do |format|
    format.html
    format.csv do
      @results.first.each do |res|
        send_data(
          generate_csv([
            ["Lab No","Assay","Batch","Cuttoff"],
            [res.lab_id, res.kit, res.batch_number, res.cutoff]
          ]),
          :filename => "my_data-#{Time.now.to_date.to_s}.csv",
          :type => 'text/csv'
        )

像这样调用方法

first

是不对的：

@results.first.each | res |…

？这会出现错误msg:

当您没有预料到它时，您有一个nil对象

此代码的目的是将结果导出为csv格式。
无论是
@results
还是
first
都是
nil
。请检查以确保这些已填充