How to seed a Rails database with a CSV file

1. Setup

First, Create a folder inside of lib called seeds

Put your CSV file example.csv into the lib/seeds folder. In the example below, the file is called real_estate_transactions.csv

Make sure you've created a resource with the appropriate columns to match your seed data. The names don't have to match up.

2. Read in a CSV file

Add the following lines to your seed.rb file:

require 'csv'

csv_text = File.read(Rails.root.join('lib', 'seeds', 'real_estate_transactions.csv'))
puts csv_text

The first line requires the Ruby CSV library we need to properly parse the CSV data. The next line reads in the CSV file into a variable. The last line prints the contents of the variable. When you run rake db:seed you should see a wall of text representing your CSV data. It's a first step, but we've still got a lot of work to do.

We'll keep building off this code until we've created a working seeds file. You should be able to run rake db:seed at the end of each step

3. Parse the CSV

require 'csv'

csv_text = File.read(Rails.root.join('lib', 'seeds', 'real_estate_transactions.csv'))
csv = CSV.parse(csv_text, :headers => true, :encoding => 'ISO-8859-1')
puts csv

The new line converts the CSV file into a structure that Ruby can read. The :headers => true option tells the parser to ignore the first line of the CSV file.

4. Looping through the parsed data

require 'csv'

csv_text = File.read(Rails.root.join('lib', 'seeds', 'real_estate_transactions.csv'))
csv = CSV.parse(csv_text, :headers => true, :encoding => 'ISO-8859-1')
csv.each do |row|
  puts row.to_hash
end

This new addition loops through the entire CSV file and converts each row of the document into a hash. The headers of the CSV file will be used as keys for the hash because we added the :headers => true option in our previous step.

5. Create a database object from each row

require 'csv'

csv_text = File.read(Rails.root.join('lib', 'seeds', 'real_estate_transactions.csv'))
csv = CSV.parse(csv_text, :headers => true, :encoding => 'ISO-8859-1')
csv.each do |row|
  t = Transaction.new
  t.street = row['street']
  t.city = row['city']
  t.zip = row['zip']
  t.zip = row['zip']
  t.state = row['state']
  t.beds = row['beds']
  t.sq_feet = row['sq_feet']
  t.category = row['type']
  t.sale_date = row['sale_date']
  t.price = row['price']
  t.lat = row['latitude']
  t.lng = row['longitude']
  t.save
  puts "#{t.street}, #{t.city} saved"
end

puts "There are now #{Transaction.count} rows in the transactions table"