Difference of Squares: Exercism/Project Euler problem

difference_of_squares.rb

class Squares
  def initialize(number)
  	@number = number
  end

  def square_of_sum
    (1..@number).to_a.sum ** 2
  end

  def sum_of_squares
    (1..@number).to_a.map! { |number| number ** 2 }.sum
  end

  def difference
    square_of_sum - sum_of_squares
  end
end