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    gt  true  dadadad asdasd net  is an int    gt  false

User · Answer

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

User · Answer

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

User · Answer

You can use the is a  method   gt  gt  1 is a  Integer   gt  true  gt  gt   dadadad asdasd net  is a  Integer   gt  false  gt  gt  nil is a  Integer   gt  false

User · Answer

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

User · Answer

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

User · Answer

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   amp  amp  s match   com       puts  It s a  com  else   puts  It s not  end

User · Answer

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  lt  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

User · Answer

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     gt  14  0014 56  to f     gt  14 56  0 0  to f     gt  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       gt  I m a float  not a float     I m a float     I m not a float or the 0 0 float       gt   I m not a float or the 0 0 float    EDIT2   be careful  the 0 integer value is not falsey it s truthy    0    gt  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   gt  12

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

You can use triple equal   if Integer     21      puts  21 is Integer  end

[ruby] Checking if a variable is an integer

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