The Normal Way

Ruby build-in supports CSV generation as CSV is so simple to compose. We can convert a 2-D array to a csv string like folllowing:

require 'csv'
arr = [['a', 'b', 'c'], ['1', '2', '3']]
arr.map(&:to_csv).join

And exporting CSV is easy in rails. Let’s see the following snippet:

def index
  @products = Product.order(:name)
  respond_to do |format|
    format.html
    format.csv { send_data @products.to_csv }
  end
end

See more about export csv in rails here

I’m lazy

However, I’m a lazy man. I even don’t want to prepare 2-D array.

In most cases, we have rendered the table in the view already. We have done some translations or formats in the view. And I don’t want to move the view code to the controller just for exporting.

Re-use the view

So, how about re-use the table in the view? I find out that render_to_string can help me do the job.

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def generate_csv_data(template = nil)
  template ||= "#{controller_name}/#{action_name}.html.slim"
  content = render_to_string(template)
  doc =  Nokogiri::HTML(content)

  table =  doc.at_css('table')
  data = table.css('tr').map do |r|
    r.css('td,th').map(&:text).to_csv
  end.join

  # Convert from utf8 to gbk to make it compatible with Windows Office Excel
  # And Mac number can work with GBK too
  data = data.encode('GBK', undef: :replace, replace: "")
end

# Respond csv file when csv format requested
format.csv { send_data generate_csv_data }

Here I get the view page as a string. And extract the table in the string with nokogiri. We can also convert it into an excel easily. See full codes here

Inspired by excelinator. But sadly, the excel exported by excelinator can not be opened with Number on my Mac. So I write a version to export csv.