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How to Export to CSV with Ruby on Rails
So, you need to export a CSV.
As with everything in Ruby on Rails, it's really easy to do this.
I will walk through how I built this feature to export sales leads on another Rails app of mine. But this same approach can be applied to any data you want to export as a CSV file.
We are going to build an endpoint that a user can navigate to, that will trigger a download of the CSV file.
The idea is, they land on a route like this
https://example.com/export/leads.csv and we start a download instead of rendering a normal page.First we need to create a route that we point the user to.
Add something like this to your
config/routes.rb file:get 'leads/export', to: 'leads#export'Change the name of your controller to whatever you want. Same with the method name. I went with
export because that makes it clear what this method is responsible for.Rails will expect the leads controller to be defined at
app/controllers/leads_controller.rb, let's create that.Initially, the contents of this controller should look something like this.
require 'csv'
class LeadsController < ApplicationController
def export
@leads = Leads.where(organization_id: current_user.organization_id)
respond_to do |format|
format.csv do
response.headers['Content-Type'] = 'text/csv'
response.headers['Content-Disposition'] = "attachment; filename=leads.csv"
end
end
end
endWe need our
export method to do a few things here.First let's pull the data. We'll need to build a query and save the results to an instance variable.
@leads = Leads.where(organization_id: current_user.organization_id)Next we have to convert the result of this query into the CSV format.
At the top of our controller let's import the built-in Rails
csv library:require 'csv'And now we can format our controller to respond when CSV is requested. Rails uses the
respond_to method to allow controller endpoints to respond to multiple formats. You will see a lot of endpoints that respond with HTML, JSON, and even XML.Here's what those formats would normally look like.
respond_to do |format|
format.html
format.json { render json: @leads.to_json }
format.xml { render xml: @leads.to_xml }
endWe'll need to slightly modify this to return CSV data.
Our version will instead respond to
format.csv:respond_to do |format|
format.csv do
response.headers['Content-Type'] = 'text/csv'
response.headers['Content-Disposition'] = "attachment; filename=leads.csv"
render template: "path/to/index.csv.erb"
end
endThis means when someone makes a request to our URL, which was
https://example.com/export/leads.csv, the tailing leads.csv extension tells our server to respond with the csv format.Also, these Content-Type headers tell the browser that we are returning a CSV file to download.
Our backend is fully wired up to export CSV for the user.
Now we need to generate the actual CSV file. The controller will automatically render the template found at
app/views/leads/export.csv.erb. Let's create that, and then here's what it will look like:
<%- headers = ['Email', 'Date'] -%>
<%= CSV.generate_line headers %>
<%- @leads.each do |lead| -%>
<%= CSV.generate_line([lead.data['email'], lead.created_at]) -%>
<%- end -%>Formatting a CSV file is very straightforward in Rails. We just need to call
CSV.generate_line to add a row.First we declare a variable called
headers, and store the headers of our CSV file.<%- headers = ['Email', 'Date'] -%>Next we generate the first row for these headers with this call:
<%= CSV.generate_line headers %>And last, we loop through our query result and again generate a row for each lead:
<%- @leads.each do |lead| -%>
<%= CSV.generate_line([lead.data['email'], lead.created_at]) -%>
<%- end -%>And that's it.
Now we have an endpoint that a user can access to download their data as a CSV. You can point users to this endpoint with a button and the download should begin automatically.
Something like this should do the trick!
<a href="/leads/export.csv">Export CSV</a>Of course, replace the query I used and pull whatever records you want in your controller.
Pass
CSV.generate_line() as many arguments as you want columns, and don't forget to pass headers in the first line to match!30