FxPotato

The Foreign Exchange currency rates looker-upper. Potato style.

Uses last daily feed from European Central Bank, and exposes a simple interface to get the conversion rates for one currency to another on a given day.

An example of this gem in use can be found at FxPotatoWeb. Source code for the site is here.

Available on RubyGems.org

And on DockerHub

Add this line to your application's Gemfile:

gem 'fxpotato'

And then execute:

$ bundle

Or install it yourself as:

$ gem install fxpotato

Or to just play around with the CLI, using docker, pull the latest image:

$ docker pull angrypotato/fx-potato

And run it like this:

$ docker run angrypotato/fx-potato:latest fxpotato
Commands:
  fxpotato getrate BASE TARGET  # Gets the foreign exchange rate for the give...
  fxpotato help [COMMAND]       # Describe available commands or one specific...

$ docker run angrypotato/fx-potato:latest fxpotato getrate GBP USD -d 2017-06-02
Exchange rate from GBP(0.87268) to USD(1.1217) on 2017-06-02: 1.2853508731722967

FxPotato takes rates from the ECB website. It then saves this data into a rates.xml file under the data directory in the root of your project. To configure either of those destinations, set the corresponding environment variables: FXPOTATO_DATA_DIR and DATA_FILE.

To change the feed, set the FXPOTATO_DATA_SOURCE_URL environment variable to the new URL, and if the structure of the xml is different (or indeed not XML at all, which is also totes cool), set FxPotato.repo to equal an instance of a custom class of your own writing for locating rates in the new structure. Make sure to set FxPotato.repo = YourClass.new before you use the other functionality in FxPotato.

The repo class you write must implement the find method with this signature:

def find(date = Date object, currency = Currency key, e.g. 'GBP')
  // your wonderful code here
end

If using the crontab functionality, configure your own schedule by editing the config/schedule.rb file, as per the whenever documentation.

FxPotato comes with optional crontab functionality to keep itself up to date. To enable the cron job, run the rake task rake fxpotato:update_crontab. Then verify the job is in your crontab by running crontab -l.

If you decide this was a big mistake and wish to purify your crontab of fxpotato, then run the rake task rake fxpotato:clear_crontab, and verify again.

The details of the cron job is configurable, as mentioned before, by editing the config/schedule.rb file as per the whenever documentation.

Assuming you successfully followed the install instructions, and are still reading this exciting documentation with much reckless abandon, steady yourself!

Now. Using the FxPotato gem in your app is as simple as:

FxPotato.at('GBP', 'USD', date)

The date parameter is a Date object, which will default to today if nil, and the currency keys are simply strings. The gem is case insensitive, so don't worry about that.

This will return a hash that looks like this:

{
  "date" => #<Date: 2017-06-06 ((2457911j,0s,0n),+0s,2299161j)>, // <-- a Date object
  "base" => {
    "key" => "GBP",
    "rate" => 0.87268
  },
  "target" => {
    "key" => "USD",
    "rate" => 1.1217
  },
  "rate" => 1.2853508731722967
}

If for any reason the call was unsuccessful, the root rate will be nil, and the unlocatable rate(s) will also be nil.

Get foreign exchange rates on the command line with the following command:

fxpotato getrate <base_currency> <target_currency> -d <YYYY-MM-DD>

e.g.
fxpotato getrate GBP USD -d 2017-06-02

The -d option is not required, and will default to today if not specified.

Or you can use fxpotato help getrate to get slightly more detailed help.

To run tests, run the rake task rake test, this will run unit and feature tests. If you have docker installed, you can run all tests in a container using the rake task rake docker_test. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install.

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/fxpotato. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the FxPotato project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.