Leading zeros in Ruby

I have fields hr and min, both integers in my application. For hr field, if the user enters "1" I would like Rails to automatically pad it to "01" before saving it to the database. Also for the min field if the user enter "0" it should 开发者_如何学编程put in as "00".

How can I do this?

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It'd be better to store it as an integer and just display it as you described on runtime. Every language has its own way to pad zeros - for Ruby you can use String#rjust. This method pads a string (right-justified) so that it becomes a given length, using a given padding character.

str.rjust(integer, padstr=' ') → new_str

If integer is greater than the length of str, returns a new String of length integer with str right justified and padded with padstr; otherwise, returns str.

some_int = 5
some_int.to_s.rjust(2, '0')  # => '05'
some_int.to_s.rjust(5, '0')  # => '00005'

another_int = 150
another_int.to_s.rjust(2, '0') # => '150'
another_int.to_s.rjust(3, '0') # => '150'
another_int.to_s.rjust(5, '0') # => '00150'

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You can transform the integer into a string of that kind with:

result_string = '%02i' % your_integer

This is independent from how it gets saved in the db.

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• Explanation & Examples

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This is also quite handy:

"%.2d" % integer

The resultant string will be of 2 characters and if the number is of less than 2 characters, then 0s will be present in the string

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You can't store 01 as integer. It will be converted to 1

You can store it as a string, or you can show it as a string "01"

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I like the % operator, even though it seems to have gone out of favor...

2.0.0-p247 :001 > '%02i' % 1
 => "01"
2.0.0-p247 :002 > '%2i' % 1
 => " 1"
2.0.0-p247 :003 > '%-2i' % 1
 => "1 "

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Another way to achieve this is to pad your integer at display time, using sprintf:

f = sprintf '%04d', 49
# f = "0049"

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Try this and you can change them to match

def numeric92(num)
  if num.present?
    if num < 0 && num > -1
      ('-%05d' % num) + '.' + ('%.2f' % num).split('.').last
    else
      ('%06d' % num) + '.' + ('%.2f' % num).split('.').last
    end
  else
    '000000.00'
  end
end