Possible Duplicate:
Test if a string is basically an integer in quotes using Ruby?
"1" "one"
The first string is a number, and I can just say to_i to get an integer.
The second string is also a number, but I can't directly call to_i to get the desired number.
How do I check whether I can successfully convert using to_i or not?
There's an Integer method that unlike to_i will raise an exception if it can't convert:
>> Integer("1")
=> 1
>> Integer("one")
ArgumentError: invalid value for Integer(): "one"
If you don't want to raise an exception since Ruby 2.6 you can do this:
Integer("one", exception: false)
If your string can be converted you'll get the integer, otherwise nil.
The Integer method is the most comprehensive check I know of in Ruby (e.g. "09" won't convert because the leading zero makes it octal and 9 is an invalid digit). Covering all these cases with regular expressions is going to be a nightmare.
rescue nil can be avoided by using Integer("one", exception: false). See my answer here: stackoverflow.com/a/54022892/4469336
'09' doesn't have to error, at least anymore: Integer() takes an optional second positional argument for base, so Integer('09', 10) would give you 9