Convert JSON Epoch to DateTime in Ruby for Conversion to CSV File

Hello Stack Overflow Friends,

We use an email metric API that returns data requested in JSON. What I am attempting to do is convert the JSON to a CSV file in Ruby (which I have been able to successfully do using the json-converter gem). But, obviously JSON returns date/time fields in Epoch which is useless to most people. Therefore, I'm trying to figure out 2 things:

1) How to appropriately convert Epoch into a more human-readable date/time for the CSV file, and

2) Where along the way in my Ruby code do I need to attempt to do this - before the JSON to CSV conversion or after?

Here's the sample code so far:

JSON Response

{
  "data": [
    {
      "id": 571823,
      "subCommunityId": 2,
      "emailName": "Email Name",
      "fromName": "John Doe",
      "fromAddress": "[email protected]",
      "subjectLine": "This is my subject",
      "preHeader": "",
      "categoryName": "General Communication",
      "sentCount": 15678,
      "scheduledDateTimestamp": 1504889858000,
      "actualSendTimestamp": 1504889858000,
      "dateAdded": 1504889859576
    }
  ],
  "startAt": 0,
  "maxResults": 1000,
  "total": 1
}

Ruby Script - JSON to CSV

require 'json_converter'
converter = JsonConverter.new
json = File.read("emailresponse.json")
converter.write_to_csv(json, "emailreporting.csv")

Any thoughts on how best to do this are welcome.

Solution

Actually, Ruby already can build CSV.

require 'json'
require 'csv'

json = '{
  "data": [
    {
      "id": 571823,
      "subCommunityId": 2,
      "emailName": "Email Name",
      "fromName": "John Doe",
      "fromAddress": "[email protected]",
      "subjectLine": "This is my subject",
      "preHeader": "",
      "categoryName": "General Communication",
      "sentCount": 15678,
      "scheduledDateTimestamp": 1504889858000,
      "actualSendTimestamp": 1504889858000,
      "dateAdded": 1504889859576
    }
  ],
  "startAt": 0,
  "maxResults": 1000,
  "total": 1
}'
hash = JSON.parse(json)

CSV.open('emailreporting.csv', 'w') do |csv| 
  # write headers row
  csv << hash['data'].first.keys 

  # write data rows
  hash['data'].each do |data| 
    data['scheduledDateTimestamp'] = Time.at(data['scheduledDateTimestamp'] / 1000)
    data['actualSendTimestamp'] = Time.at(data['actualSendTimestamp'] / 1000) 
    data['dateAdded'] = Time.at(data['dateAdded'] / 1000) 
    csv << data.values  
  end
end

Building CSV manually gives some advantages:

using Ruby's standard library rather than some little-known gem
more control during building csv