Ruby on Rails: How do you add add zeros in front of a number if it's under 10?

Question

I'm looking to convert single digit numbers to two-digit numbers like so:

9 ==> 09
5 ==> 05
12 == 12
4 ==> 04

I figure I could put a bunch of if-else statements (if number is under 10, then do a gsub) but figure that's horrible coding. I know Rails has number_with_precision but I see that it only applies to decimal numbers. Any ideas on how to convert single-digits to two-digits?

Answer 1

there is no language that supports numbers with leading zero. You need to convert number to string and if < 10 add 0 in front of it.

Answer 2

Did you mean sprintf '%02d', n?

irb(main):003:0> sprintf '%02d', 1
=> "01"
irb(main):004:0> sprintf '%02d', 10
=> "10"

You might want to reference the format table for sprintf in the future, but for this particular example '%02d' means to print an integer (d) taking up at least 2 characters (2) and left-padding with zeros instead of spaces (0).

Answer 3

how about "%02d" % 9? see http://www.ruby-doc.org/core/classes/String.html#M000770 and http://www.ruby-doc.org/core/classes/Kernel.html#M005962 .

Answer 4

TRY THIS IT SHOULD WORK

abc= 5
puts "%.2i" %abc   >> 05


abc= 5.0
puts "%.2f" %abc   >> 5.00

Answer 5

A lot of people using sprintf (which is the right thing to do), and I think if you want to do this for a string it's best to keep in mind the rjust and ljust methods:

"4".rjust(2, '0')

This will make the "4" right justified by ensuring it's at least 2 characters width and to pad it with '0'. ljust does the opposite.