wvdschel wvdschel - 1 year ago 117
Ruby Question

Safe integer parsing in Ruby

I have a string, say

, and I want to convert it to

I know you can simply do
, but that converts
, which is not the effect I have in mind. I want it to blow up in my face when I try to convert something invalid, with a nice and painful
. Otherwise, I can't distinguish between a valid
and something that just isn't a number at all.

EDIT: I was looking for the standard way of doing it, without regex trickery.

Answer Source

Ruby has this functionality built in:

Integer('1001')                                    # => 1001  
Integer('1001 nights')  
# ArgumentError: invalid value for Integer: "1001 nights"  

As noted in answer by Joseph Pecoraro, you might want to watch for strings that are valid non-decimal numbers, such as those starting with 0x for hex and 0b for binary, and potentially more tricky numbers starting with zero that will be parsed as octal.

Ruby 1.9.2 added optional second argument for radix so above issue can be avoided:

Integer('23')                                     # => 23
Integer('0x23')                                   # => 35
Integer('023')                                    # => 19
Integer('0x23', 10)
# => #<ArgumentError: invalid value for Integer: "0x23">
Integer('023', 10)                                # => 23
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