string - Safe integer parsing in Ruby

Question

I have a string, say '123', and I want to convert it to the integer 123.

I know you can simply do some_string.to_i, but that converts 'lolipops' to 0, 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 Exception. Otherwise, I can't distinguish between a valid 0 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 1

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