ContextEval

provide Object#context_eval

Installation

Add this line to your application's Gemfile:

gem 'context_eval'

And then execute:

$ bundle

Or install it yourself as:

$ gem install context_eval

Usage

class Notification < ActiveRecord::Base
  belongs_to :user
  belongs_to :notifiable, polymorphic: true

  delegate :notification_config, to: :notifiable

  def title
    notifiable.context_eval(notification_config[:title]) || raise
  end

  def message
    notifiable.context_eval(notification_config[:message])
  end
end

module Notifiable
  extend ActiveSupport::Concern

  included do
    config_accessor :notification_config, instance_writer: false # ActiveSupport::Configurable

    has_one :notification, as: :notifiable, dependent: :destroy, class_name: '::Notification'

    after_create do
      self.create_notification!(user: context_eval(notification_config[:send_to]))
    end
  end
end

class Nice < ActiveRecord::Base
  include Notifiable

  self.notification_config = {
    title: 'Nice!',
    send_to: -> { article.user }
  }

  belongs_to :article
end

class Comment < ActiveRecord::Base
  include Notifiable

  self.notification_config = {
    title: -> { "#{body[0..20]}..." },
    message: :body,
    send_to: -> { article.user }
  }

  belongs_to :article
end

<ul>
  <% @notifications.each do |notification| %>
    <li>
      <h3><%= notification.title %></h3>

      <% if notification.message.present? %>
        <p><%= notification.message %></p>
      <% end %>
    </li>
  <% end %>
</ul>

Detail

class User
  attr_accessor :name

  def initialize(name)
    @name = name
  end
end

user = User.new('john')

# Symbol
user.context_eval(:name) #=> john

# Proc
proc_arg = Proc.new { "Mr. #{name}" }
user.context_eval(proc_arg) #=> Mr. john

# Proc and args
proc_arg = Proc.new { |age| "Mr. #{name}, #{age} years old." }
user.context_eval(proc_arg, 30) #=> Mr. john, 30 years old.

# Lambda
lambda_arg = -> { "Mr. #{name}" }
user.context_eval(lambda_arg) #=> Mr. john

# Lambda and args
lambda_arg = -> (age) { "Mr. #{name}, #{age} years old." }
user.context_eval(lambda_arg, 30) #=> Mr. john, 30 years old.

# String
user.context_eval('Hey john') #=> Hey John

# Nil
user.context_eval(nil) #=> nil

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/context_eval. 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.

Code of Conduct

Everyone interacting in the ContextEval project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.

context_eval