How to cleanly verify if the user input is an integer in Ruby?

Question

I have a piece of code where I ask the user to input a number as an answer to my question. I can do to_i but tricky/garbage inputs would escape through to

Answer 1

Use Kernel#Integer

The Kernel#Integer method will raise ArgumentError: invalid value for Integer() if passed an invalid value. The method description says, in part:

[S]trings should be strictly conformed to numeric representation. This behavior is different from that of String#to_i.

In other words, while String#to_i will forcibly cast the value as an integer, Kernel#Integer will instead ensure that the value is already well-formed before casting it.

Examples Simulating Behavior of Integer(gets)

Integer(1)
# => 1

Integer('2')
# => 2

Integer("1foo2\n")
# => ArgumentError: invalid value for Integer(): "1foo2\n"