Implementing an even Fibonacci number algorithm

In this section, we are going to solve a mathematical challenge that asks us to find even Fibonacci numbers. The full question is: by considering the terms in the Fibonacci sequence whose values do not exceed 4 million, find the sum of the even-valued terms.

Since this is a fairly straightforward problem (assuming that you are familiar with the Fibonacci sequence), we're going to build a more exhaustive solution to further our understanding of Ruby. We're not going to write a one-line code answer for this problem; rather, we are going to build a class:

class Fibbing
  def initialize(max)
    @num_1 = 0
    @i = 0
    @sum = 0
    @num_2 = 1
    @max = max
  end
  def even_fibonacci
    while @i<= @max
      @i = @num_1 + @num_2
      @sum += @i if@i % 2 == 0
      @num_1 = @num_2
      @num_2 = @i
    end
   @sum
  end
end 

In this code...