How to parse a CSV file, update a field, then save - ruby

Question

I need to read a CSV file, update a field, then save the changes. I have everything working fine except saving my changes to the field I'm updating:
require 'csv'
#parsed_file = CSV::Reader.parse(File.open("#{RAILS_ROOT}/doc/some.csv"))
#parsed_file.each_with_index do |row, x|
address = row[5]
l = Location.address_find(address)
if l != nil
puts "#{l.name} at #{l.address}"
row[14] = l.store_code
puts row[14]
else
puts "No matching address Found!!!"
end
#What do I do here? Something like this? CSV::Writer.generate(#parsed_file)
end
What do I do here? How do I save the changes I made and update the file?

Answer 1

What I would do is write the updated records to a new file and then, if you want, after you have finished your program can delete the old file and rename the new file to have the original file name.
To do this I would open the output file at the top of your code, outside the each_with_index loop. e.g.
csv_out = CSV::Writer.generate(File.open('new.csv', 'wb'))
Then inside your each_with_index loop you can write the current row to the new file like this:
csv_out << row
Then at the end you can close the new file:
csv_out.close
As mentioned in the comments, CSV::Writer is no longer in the standard library. An equivalent version of the code using the newer CSV.foreach (for reading) and CSV.open (for writing) is:
CSV.open("path/to/updated_file.csv", "wb") do |csv_out|
CSV.foreach("#{RAILS_ROOT}/doc/some.csv") do |row|
address = row[5]
l = Location.address_find(address)
if l != nil
puts "#{l.name} at #{l.address}"
row[14] = l.store_code
puts row[14]
else
puts "No matching address Found!!!"
end
csv_out << row
end
end