Checking if a variable is an integer

You can use the is_a? method

>> 1.is_a? Integer
=> true
>> "[email protected]".is_a? Integer
=> false
>> nil.is_a? Integer
=> false

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

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