test

test.rb

def query(params)
  # this magic method prepares sql and gets correct data from DB
  # NO CHANGES HERE
  puts "Params = #{params}"
  [
    {name: "John", surname: "Doe", age: 33},
    {name: "John", surname: "Doe", age: 34},
    {name: "John", surname: "Doe", age: 35}
  ]
end

class ActiveRecord
  class << self
    def criteria
      @criteria ||= {}
    end

    def where(args)
      criteria.merge!(args)

      self
    end

    def order(order)
      criteria[:order] = order

      self
    end

    def map(&block)
      query(criteria).map(&block)
    end
  end
end

class User < ActiveRecord

end

ages = User.where(name: "John").where(surname: "Doe").order("age").map do |u|
  u[:age]
end

puts "Ages = #{ages}" # [33, 34, 35]