Converting an integer to a hexadecimal string in Ruby

Question

Is there a built in way to convert an integer in Ruby into its hexadecimal equivalent?

Something like the opposite of String#to_i:

"0A".to_i(16) #=>10

Like perhaps:

"0A".hex #=>10

I know how to roll my own, but it's probably more efficient to use a built in Ruby function.

Answer 1

You can give to_s a base other than 10:

10.to_s(16)  #=> "a"

Answer 2

How about using %/sprintf:

i = 20
"%x" % i  #=> "14"

Answer 3

To summarize:

p 10.to_s(16) #=> "a"
p "%x" % 10 #=> "a"
p "%02X" % 10 #=> "0A"
p sprintf("%02X", 10) #=> "0A"
p "#%02X%02X%02X" % [255, 0, 10] #=> "#FF000A"

Answer 4

Here's another approach:

sprintf("%02x", 10).upcase

see the documentation for sprintf here: http://www.ruby-doc.org/core/classes/Kernel.html#method-i-sprintf

Answer 5

Just in case you have a preference for how negative numbers are formatted:

p "%x" % -1   #=> "..f"
p -1.to_s(16) #=> "-1"