example.rb

# DbAdapter provides access to the underlaying DB layer:
#   DbAdapter.new.fetch_records(User, name: "Ivan", active: true)   # => [ <#User>, <#User>, .... ]
#
class DbAdapter
  def fetch_records(klass, conditions)
    # .... returns an array of records
  end
end

# This is our "ActiveRecord" class
class User
  def self.table_name
    "users"
  end

  # TODO: implement "where" method
end

class Relation
  # TODO: implement this class
end

# TODO: the code below should work just like ActiveRecord in Rails
relation = User.where(name: "Ivan").where(active: true)
relation.to_a    # => [ <#User>, <#User>, .... ]