Checking if a variable is an integer

Question

Does Rails 3 or Ruby have a built-in way to check if a variable is an integer?

For example,

1.is_an_int #=> true
\"dadadad@asdasd.net\".is_an_int          


        

Answer 1

Probably you are looking for something like this:

Accept "2.0 or 2.0 as an INT but reject 2.1 and "2.1"

num = 2.0

if num.is_a? String num = Float(num) rescue false end

new_num = Integer(num) rescue false

puts num

puts new_num

puts num == new_num

Answer 2

You can use the is_a? method

>> 1.is_a? Integer
=> true
>> "dadadad@asdasd.net".is_a? Integer
=> false
>> nil.is_a? Integer
=> false

Answer 3

If you want to know whether an object is an Integer or something which can meaningfully be converted to an Integer (NOT including things like "hello", which to_i will convert to 0):

result = Integer(obj) rescue false

Answer 4

Use a regular expression on a string:

def is_numeric?(obj) 
   obj.to_s.match(/\A[+-]?\d+?(\.\d+)?\Z/) == nil ? false : true
end

If you want to check if a variable is of certain type, you can simply use kind_of?:

1.kind_of? Integer #true
(1.5).kind_of? Float #true
is_numeric? "545"  #true
is_numeric? "2aa"  #false

Answer 5

There's var.is_a? Class (in your case: var.is_a? Integer); that might fit the bill. Or there's Integer(var), where it'll throw an exception if it can't parse it.