Shield

Shield is a policies clean API for using in Rails applications. The intention is to have an easy way to use policies inside Rails applications with a clean and well defined API.

The basic idea is to have some PORO to handle read operations without in case those operations get a little bit complex.

The following resources brought some inspirations to the lib:

Rails - the Missing Parts - Policies

Doman Driven Rails - Yan Pritzker

7 Patterns to Refactor Fat ActiveRecord Models

Installation

Add this line to your application's Gemfile:

gem 'shield'

And then execute:

$ bundle

Or install it yourself as:

$ gem install shield

Usage

Simple case

class IsActiveUser
  def initialize(user)
    @user = user
  end

  def validate
    user.email_confirmed? && user.last_login_at > 14.days.ago
  end

  private

  attr_reader :user
end

class Subscriber
  include Shield

  def subscribe(user)
    policies.with(IsActiveUser.new(user)).apply
  end
end

Throwing exceptions

When calling apply! instead of apply shield will generate an exception dynamically for you with the error message that you specified the name will be based on the policy name plus the word error; ex. IsActiveUserError

class IsActiveUser
  attr_reader :error

  def initialize(user, error)
    @error = error
    @user = user
  end

  def validate
    user.email_confirmed? && user.last_login_at > 14.days.ago
  end

  private

  attr_reader :user
end

class Subscriber
  include Shield

  def subscribe(user)
    policies.with(IsActiveUser.new(user, 'Policy failed')).apply!
  end
end

Contributing

1. Fork it ( https://github.com/[my-github-username]/shield/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request