NCCO

Nexmo Call Control Objects (NCCOs) allow you to decide with your code what happens in a phone call which you've placed or received using Nexmo's Voice API.

If you make a mistake in your NCCO (for example, you miss out a required parameter or misspell something), the call will fail.

This gem allows you to validate your NCCOs before you send them to Nexmo, giving you a tighter feedback loop and helping you to catch errors earlier, before they hit production (for example when you run your tests).

Add this line to your application's Gemfile:

gem "ncco", "~> 0.1.0"

Next, install the gem by running:

bundle

Nexmo Call Control Objects (NCCOs) are JSON arrays of objects. In Ruby, you'll build a Ruby array of hashes, where each hash represents an "action" in your call, and then you'll send it to Nexmo as JSON:

say_hello = {
  action: "talk",
  text: "Hello there! You're through to Acme Widgets. Leave a message after the tone. Press star or hang up when you're done.",
}

record_message = {
  action: "record",
  endOnKey: "*",
  beepStart: true,
  eventUrl: "https://acmewidgets.com/nexmo/recordings",
  eventMethod: "POST",
  format: "mp4"
}

ncco = [say_hello, record_message]
render json: ncco

The eagle-eyed among you will have noticed that there's a mistake in our example above: Nexmo doesn't support the mp4 format for recordings! This would lead to an error, and a bad experience for our users 😭

But there's a better way:

require "ncco"

render json: NCCO.build(ncco)

This will still fail - our NCCO is invalid! - but our application will let us know ahead of time:

NCCO.build(ncco)
# NCCO::InvalidActionError (The 2nd action is invalid: format must be one of: mp3, wav,
# ogg, eventUrl must be a valid HTTP or HTTPS URL)

This allows you to catch errors earlier and easily handle them with your usual exception tracking tools (for example Sentry).

After checking out the repo, run bin/setup to install dependencies.

Then, run rake spec to run the tests and rake lint to check the code style with Rubocop.

You can also run bin/console for an interactive prompt that will allow you to experiment with the gem.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

NCCO "actions" are defined using schemas in lib/ncco/schemas, implemented using dry-validation.

To tweak how we validate an action (for example to add a new attribute or change how an existing one is validated), just update the action's corresponding schema. Testing is easy thanks to our allow_value, require_attribute and allow_blank_values matchers - see the existing tests for an example.

If you want to add support for a new action, you'll need to crerate a new schema in lib/ncco/schemas, require it and add it to SCHEMAS_BY_TYPE in lib/ncco.rb and write some tests.

Bug reports and pull requests are welcome on GitHub at https://github.com/timrogers/ncco. 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 Ncco project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.