Question

for example

str = 'f01288c2' #a hexadecimal string
bin = str.to_i(16).to_s(2).rjust(str.length + (64 - (str.length % 64)), '0')

so the size of the binary string is always the multiply of 64.
The problem here is, the str.length is the length before it’s converted into binary. I need the length of the string after to_s(2). How do I access the return value of the to_s(2)?

Update
I wonder if there is a one chain solution.

Answer 1

The one-line solution would use Kernel#tap and str.replace:

ruby > str = 'f01288c2' #a hexadecimal string
 => "f01288c2" 
ruby > bin = str.to_i(16).to_s(2).rjust(str.length + (64 - (str.length % 64)), '0')
 => "0000000000000000000000000000000011110000000100101000100011000010" 
ruby > bin = str.to_i(16).to_s(2).tap { |str| str.replace str.rjust(str.length + (64 - (str.length % 64)), '0') }
 => "11110000000100101000100011000010"