Example of the left-side completion method of a string in Ruby

Recently, there is a need to display the number as a fixed number of digits. If the number of digits is insufficient, add it as zero.

For example, five digits:
Copy codeThe Code is as follows:
3-> 00003
292-> 00292
12422-> 12422
Ruby is easy to implement.
Copy codeThe Code is as follows: irb> "% 05d" % 12422
"12422"
Irb> "% 05d" % 22
"00022"

The above method is basically a standard practice. If the String is processed directly, you can also use String # Processing ust:
"12422". Must ust (5, '0') => "12422"
"22". Must ust (5, '0') => "00022"

Appendix: another article

The project uses the algorithm of padding between the left and right strings, and finally finds that rails can implement such functions, saving unnecessary trouble. The example should be simple and easy to understand.
Copy codeThe Code is as follows:
>>> A = 22
>>> S = str (a). Must ust (4, '0 ')
>>> Print s
0022
>>> A = 2222
>>> S = str (a). Must ust (4, '0 ')
>>> Print s
2222