Help refactoring this nasty Ruby if/else statement

Question

So I have this big, hairy if/else statement. I pass a tracking number to it, and then it determines what type of tracking number it is.

How can I simplify this thing? Sp

Answer 1

I believe this is sufficiently complex to deserve its own method.

BTW, if the length is 20 then the original function returns whatever check_response(n) returns, yet then attempts (and will always fail) to return 'usps'.

@lenMap = Hash.new false
@lenMap[17] = 'dhlgm'
@lenMap[13] = @lenMap[20] = @lenMap[22] = @lenMap[30] = 'usps'
@lenMap[12] = @lenMap[15] = @lenMap[19] = 'fedex'
@lenMap[10] = @lenMap[11] = 'dhl'       

def ts n
  len = n.length
  return false if len < 8
  case n
    when /^.Z/
      return 'ups'
    when /^Q/
      return 'dhl'
    when /^96....................$/
      return 'fedex'
    when /^[HK]..........$/
      return 'ups'
  end
  return check_response n if len == 18 or len == 20
  return @lenMap[len]
end

# test code...
def check_response n
  return 'check 18/20 '
end
%w{ 1Zwhatever Qetcetcetc 9634567890123456789012 H2345678901
    K2345678901 hownowhownowhownow hownowhownowhownow90
    12345678901234567
    1234567890123
    12345678901234567890
    1234567890123456789012
    123456789012345678901234567890
    123456789012
    123456789012345
    1234567890123456789
    1234567890
    12345678901 }.each do |s|
      puts "%32s  %s" % [s, (ts s).to_s]
    end