Trinary

trinary.rb

class Trinary
  def initialize(string)
    @trinary_number = string
  end

  def to_decimal
    return 0 if contains_any_non_digit?

    numbers_paired_with_powers.map do |pair|
      pair[0].to_i * 3**pair[1]
    end.inject(:+)
  end

  private

  def contains_any_non_digit?
    @trinary_number =~ /\D/
  end

  def numbers_paired_with_powers
    powers = 0..@trinary_number.size - 1
    @trinary_number.chars.zip(powers.to_a.reverse)
  end
end