How can I see if the string is numeric?

问题

I have the string "08" and I like to know if this string is numeric. How can I do it in Rails 3.1?

回答1:

Another way to do this is to leave it up to ruby to determine it:

begin
    Float(string)
    # String is numeric
rescue ArgumentError, TypeError
    # String is not numeric
end

回答2:

You can use a regular expression:

str = "08"
if str =~ /^-?(\d+(\.\d+)?|\.\d+)$/
  # string is numeric
else
  # string is not
end

回答3:

If you are wanting to validate user input it would be just as simple to only allow them to input numbers with something like validates_format_of :string, :with => /[0-9]/.

来源：https://stackoverflow.com/questions/9469587/how-can-i-see-if-the-string-is-numeric