Ruby on Rails：如果数字小于 10，如何在数字前添加零？
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Ruby on Rails: How do you add add zeros in front of a number if it's under 10?
提问by sjsc
I'm looking to convert single digit numbers to two-digit numbers like so:
我希望将一位数字转换为两位数字，如下所示：
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?
我想我可以放一堆 if-else 语句（如果数字小于 10，那么做一个 gsub）但我认为这是可怕的编码。我知道 Rails 有 number_with_precision，但我看到它只适用于十进制数。关于如何将个位数转换为两位数的任何想法？
回答by Ryan Bigg
A lot of people using sprintf(which is the right thing to do), and I think if you want to do this for a stringit's best to keep in mind the rjustand ljustmethods:
很多人都在使用sprintf（这是正确的做法），我认为如果您想对字符串执行此操作，最好记住rjust和ljust方法：
"4".rjust(2, '0')
This will make the "4"right justified by ensuring it's at least 2characters long and pad it with '0'. ljustdoes the opposite.
这将"4"通过确保它至少是2字符长并用'0'. ljust相反。
回答by Mark Rushakoff
Did you mean sprintf '%02d', n?
你的意思是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 sprintfin 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).
您可能希望在将来引用格式表sprintf，但对于此特定示例，这'%02d'意味着打印一个整数 ( d)，该整数至少占 2 个字符 ( 2)，并使用零而不是空格 ( 0)向左填充。
回答by ax.
回答by Salil
Try this, it should work:
试试这个，它应该可以工作：
abc= 5
puts "%.2i" %abc >> 05
abc= 5.0
puts "%.2f" %abc >> 5.00
