Predicator

Predicator is a safe (does not eval code), admin or business user facing predicate engine. It turns a string predicate like "score > 600 or (score > 580 and monthly_income > 9000)" along with a supplied context into a true or false. This predicate can be stored as an attribute of a model (ex: an Offer model could store a predicate indicating if it is available to a customer).

Usage

Simple usage:

require "predicator"

Predicator.evaluate "score > 600 or (score > 580 and income > 9000)", score: 590 # false

Predicator.evaluate "score > 600 or (score > 580 and income > 9000)", score: 590, income: 9500 # true

Example usage with a model:

class Customer
  ...
  def to_hash
    {
      ...
      score: score,
      income: income,
      ...
    }
  end
end

class Offer
  attr_accessor :available_predicate

  ...

  def available_to? customer
    Predicator.evaluate available_predicate, customer.to_hash
  end
end

Installation

Add this line to your application's Gemfile:

gem "predicator"

And then execute:

$ bundle

Or install it yourself as:

$ gem install predicator

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test (or just rake) 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.

Contributing

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

License

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