Question

So, I have Ruby on Rails application. Blank for now. And let me say right from the beginning that most of my experience is from Java, so I might be thinking not the way RoR devs do. 🙂

What I need to do is to create some Data Access Layer, say it will be access users, so let it be
UserDAO.rb which will be basically then using ActiveRecord or directly accessing the database or accessing or some key-value storage or anything else I can think of.

Technically, as we don’t have interfaces in Ruby, I can make UserDAO.rb to “have” the implementation (basically, I am talking about composition), which may be anything we need, say UserDAOActiveRecord.rb or UserDAOMongo.rb or anything else like that. UserDAO.rb will basically call the methods of the implementation and that’s it. Should be easy to switch between implementations.

While it does sound like a possible solution, I am looking forward to hear what are the best practices for this problem in the Ruby world. Thanks!

Answer 1

You will have to look for a Ruby Class other than ActiveRecord (which as pointed out is an Object Relational Mapper, so has no separate data access layer).

You might want to look at: https://github.com/jeremyevans/sequel

You could create a class, Person, which contains methods which use an instance of Sequel to talk to the database.

This untested code demonstrates why this might not be a great idea:

class Person
  attr_reader :first_name, :last_name

  DataSource = Sequel.sqlite('my_app.db')[:people]

  def initialize(record)
    @first_name = record.first_name
    @last_name = record.last_name
  end

  # Find a record from the database and use it to initialize a new Person object 
  def self.find_by_id(id)
    self.new(Table.where(:id => id))
  end
end