hash_param

hash_param is an library that converts functions that take a single "data" argument Hash into a function that takes named, formal parameters. This allows APIs like ActionCable to be a little easier to work with.

For example, it can turn this:

class ChatChannel < ApplicationCable::Channel
  def send_message(data)
    chat_id = data['chat_id']
    author_id = data['author_id']
    body = data['body']
    # ...
  end

  def typing_status(data)
    chat_id = data['chat_id']
    user_id = data['user_id']
    status = data['status'] || 'typing'
    # ...
  end
end

into this:

class ChatChannel < ApplicationCable::Channel
  hash_param :send_message, :typing_status

  def send_message(chat_id, author_id, body)
    # ...
  end

  def typing_status(chat_id, user_id, status = 'typing')
    # ...
  end
end

It does this by looking at your method signature and filling in parameters by name from the data object. It plays nice with default parameters, keyword arguments, both optional and required, *rest and **kwrest parameters.

After named positional arguments, hash_param will try to fill named keyword arguments, then will send the rest to **kwrest if listed, and lastly, will send whats left of the data object to *args. In practice, this means you'll never get values in both *args and **kwrest.

*args parameters keep the string key names, while **kwrest hashes get their keys converted into symbols. If there are no values to pass to *args, you'll get an empty list, not a list containing an empty Hash.

If the argument list cannot be satisfied, ArgumentError is raised. Extraneous properties sent to the method are ignored if not consumed through the argument list.

Add this line to your application's Gemfile:

gem 'hash_param'

And then execute:

$ bundle

Or install it yourself as:

$ gem install hash_param

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. 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. 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.

Bug reports and pull requests are welcome on GitHub at https://github.com/metermd/hash_param.

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