ABN verfication code in Ruby

The Australian Business Number (ABN) is a self-checking series of numbers. Here is some code I used to verify ABN numbers for a job I was working on.

class ABN
    @@weight = Array[10,1,3,5,7,89,11,13,15,17,19]
  
    def initialize(abn)
      @abn = abn
    end
  
    def valid?
      self.valid?(@abn)
    end
  
    def self.valid?(abn)
      #strip ws and split on numbers
      abn_array = abn.strip.split(//)
      abn_array[0] = abn_array[0].to_i - 1
      sum = 0
      abn_array.each_index {|x|
        sum += abn_array[x].to_i * @@weight[x]
      }
      sum.remainder(89) == 0
    end
  end