Turning long fixed number to array Ruby

Is there a method in ruby to turn fixnum like 74239 into an array like [7,4,2,3,9]?

You don't need to take a round trip through string-land for this sort of thing:

def digits(n)
  Math.log10(n).floor.downto(0).map { |i| (n / 10**i) % 10 }
end

ary = digits(74239)
# [7, 4, 2, 3, 9]

This does assume that n is positive of course, slipping an n = n.abs into the mix can take care of that if needed. If you need to cover non-positive values, then:

def digits(n)
  return [0] if(n == 0)
  if(n < 0)
    neg = true
    n   = n.abs
  end
  a = Math.log10(n).floor.downto(0).map { |i| (n / 10**i) % 10 }
  a[0] *= -1 if(neg)
  a
end