Returning CSV data to the browser - revisited

2009-04-06

Back in 2006, I wrote Returning CSV data to the browser. The method I was using back then is way obsolete. Let’s use the correct way to do it. If you want to follow along, just browse over to returning-csv-data-to-the-browser-revisited and read on.

First of all, the correct way to return non HTML data to the browser is to use respond_to. Let’s do so here:

app/controllers/reports/timelines_controller.rb
 1 class Reports::TimelinesController < ApplicationController
 2   def show
 3     @timelines = Timeline.all
 4     respond_to do |format|
 5       format.csv do
 6         response.headers["Content-Type"]        = "text/csv; charset=UTF-8; header=present"
 7         response.headers["Content-Disposition"] = "attachment; filename=timeline-report.csv"
 8       end
 9     end
10   end
11 end

The rest is pretty easy. Generating the data is easy enough:

app/models/timeline.rb
 1 require "fastercsv"
 2 
 3 class Timeline < ActiveRecord::Base
 4   default_scope :order => "started_at ASC"
 5 
 6   def to_csv
 7     FasterCSV.generate_line([
 8           started_at.to_s(:db),
 9           ended_at.to_s(:db),
10           project_id]).chomp
11   end
12 end

And rendering the view? Look how easy this gets:

app/views/reports/timelines/show.csv.erb
1 Started At,Ended At,Project ID
2 <%= render :partial => @timelines %>

Notice the file’s name? show.csv.erb? The csv in the filename is what connects the respond_to call with the view.

And the final piece, the timeline partial:

app/views/reports/timelines/_timeline.csv.erb
1 <%= timeline.to_csv %>
2

Now, on to the next obsolete article in the bunch…

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