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

Answer 1

someString = "asdfasd123"
number = someString.to_i
if someString != number.to_s
  puts "oops, this isn't a number"
end

Probably not the cleanest way to do it, but should work.

Answer 2

I like Myron's answer but it suffers from the Ruby disease of "I no longer use Java/C# so I'm never going to use inheritance again". Opening any class can be fraught with danger and should be used sparingly, especially when it's part of Ruby's core library. I'm not saying don't ever use it, but it's usually easy to avoid and that there are better options available, e.g.

class IntegerInString < String

  def initialize( s )
    fail ArgumentError, "The string '#{s}' is not an integer in a string, it's just a string." unless s =~ /^\-?[0-9]+$/
    super
  end
end

Then when you wish to use a string that could be a number it's clear what you're doing and you don't clobber any core class, e.g.

n = IntegerInString.new "2"
n.to_i
# => 2

IntegerInString.new "blob"
ArgumentError: The string 'blob' is not an integer in a string, it's just a string.

You can add all sorts of other checks in the initialize, like checking for binary numbers etc. The main thing though, is that Ruby is for people and being for people means clarity. Naming an object via its variable name and its class name makes things much clearer.