Callee

This gem helps to define callable classes with strict params specification.

Installation

Add this line to your application's Gemfile:

gem 'callee'

And then execute:

$ bundle

Or install it yourself as:

$ gem install callee

Usage

To make a class callable, you need to include Callee mixin and implement call instance method. Use dry-initializer DSL to specify calling parameters and options if necessary. Here is a basic usage example:

class Power
  include Callee

  # Required parameter
  param :base

  # Option with a default value
  option :exponent, optional: true, default: -> { 2 }

  def call
    base.pow(exponent)
  end
end

Power.call(2)  # => 4
Power.call(2, exponent: 10)  # => 1024

Callable class may be used as a Proc. Compact notation in the next example is identical to [1, 2, 3].map { |value| Power.call(value) }

[1, 2, 3].map(&Power)  # => [1, 4, 9]

Since Callee mixin inherits dry-initializer DSL, type constraints and coercion will also work, as usual. Just make sure to include dry-types:

require "dry-types"

class StrictPower
  include Callee

  param :base, type: Dry::Types["strict.integer"]
  option :exponent, type: Dry::Types["strict.integer"], optional: true, default: -> { 2 }

  def call
    base.pow(exponent)
  end
end

# Let's inherit StrictPower params definition
# and override "base" with more forgiving constraint
class CoerciblePower < StrictPower
  param :value, type: Dry::Types["coercible.integer"]
end

string_values = %w[1 2 3]

string_values.map(&StrictPower)  # Will raise Dry::Types::ConstraintError
string_values.map(&CoerciblePower)  # => [1, 4, 9]

See more examples in dry-rb docs.

Development

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.

Contributing

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

License

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