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
"[email protected]".is_an_int #=> false?
This question is related to
ruby
ruby-on-rails-3
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
To capitalize on the answer of Alex D, using refinements:
module CoreExtensions
module Integerable
refine String do
def integer?
Integer(self)
rescue ArgumentError
false
else
true
end
end
end
end
Later, in you class:
require 'core_ext/string/integerable'
class MyClass
using CoreExtensions::Integerable
def method
'my_string'.integer?
end
end
I have had a similar issue before trying to determine if something is a string or any sort of number whatsoever. I have tried using a regular expression, but that is not reliable for my use case. Instead, you can check the variable's class to see if it is a descendant of the Numeric class.
if column.class < Numeric
number_to_currency(column)
else
column.html_safe
end
In this situation, you could also substitute for any of the Numeric descendants: BigDecimal, Date::Infinity, Integer, Fixnum, Float, Bignum, Rational, Complex
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.
You can use triple equal.
if Integer === 21
puts "21 is Integer"
end
In case you don't need to convert zero values, I find the methods to_i
and to_f
to be extremely useful since they will convert the string to either a zero value (if not convertible or zero) or the actual Integer
or Float
value.
"0014.56".to_i # => 14
"0014.56".to_f # => 14.56
"0.0".to_f # => 0.0
"not_an_int".to_f # 0
"not_a_float".to_f # 0.0
"0014.56".to_f ? "I'm a float" : "I'm not a float or the 0.0 float"
# => I'm a float
"not a float" ? "I'm a float" : "I'm not a float or the 0.0 float"
# => "I'm not a float or the 0.0 float"
EDIT2 : be careful, the 0
integer value is not falsey it's truthy (!!0 #=> true
) (thanks @prettycoder)
EDIT
Ah just found out about the dark cases... seems to only happen if the number is in first position though
"12blah".to_i => 12
If you're uncertain of the type of the variable (it could be a string of number characters), say it was a credit card number passed into the params, so it would originally be a string but you want to make sure it doesn't have any letter characters in it, I would use this method:
def is_number?(obj)
obj.to_s == obj.to_i.to_s
end
is_number? "123fh" # false
is_number? "12345" # true
@Benny points out an oversight of this method, keep this in mind:
is_number? "01" # false. oops!
A more "duck typing" way is to use respond_to?
this way "integer-like" or "string-like" classes can also be used
if(s.respond_to?(:match) && s.match(".com")){
puts "It's a .com"
else
puts "It's not"
end
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
Basically, an integer n is a power of three, if there exists an integer x such that n == 3x.
So to verify that you can use this functions
def is_power_of_three(n)
return false unless n.positive?
n == 3**(Math.log10(n)/Math.log10(3)).to_f.round(2)
end
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
Source: Stackoverflow.com