Split a value and units in Ruby

Question

What is the most elegant way to split a value and units, so you have:

13min.some_method["value"] = 13
13min.some_method["unit"] = "min"

I think it should use unpack or split, but I can get it to work!

Answer 1

How about String#scan:

>> "13min".scan(/\d+|[^\d]+/)
=> ["13", "min"]

Another way:

>> i = "13min" =~ /[^\d]/
=> 2
>> "13min"[0,i]
=> "13"
>> "13min"[i,"13min".length]
=> "min"

The reason String#split isn't the best is because it gets rid of the delimiter, but your two strings are butted up against each other.

Answer 2

Here's an alternative you could try (which will also work with floats and negative numbers):

s = "-123.45min"

value = s.to_f          # => -123.45
unit = s[/[a-zA-Z]+/]   # => "min"

Like Ruby's to_f and to_i method, it will just "try" to get a result. So if you don't provide a unit, unit will be nil - if you only provide a unit, value will be 0.

"123-34min"    value = 123,     unit = "min"
"min"          value = 0        unit = "min"
"-1234"        value = -1234    unit = nil
"123-foo-bar"  value = 123      unit = "foo"

P.S. Of course this assumes that you don't have any numbers in your unit.