RoR: checking for numeric value

Question

I have found a code for checking whether string is numeric. And it works fine. But I am not getting how is it working. Can anyone explain it.

    str = "12132344", str1="abcd", str2="12213234.132332"

    /^[\d]+(\.[\d]+){0,1}$/ === str  #=> true  //perfect
    /^[\d]+(\.[\d]+){0,1}$/ === str1 #=> false //perfect
    /^[\d]+(\.[\d]+){0,1}$/ === str2 #=. true  //perfect

when i change the comparison like below:

    str === /^[\d]+(\.[\d]+){0,1}$/ #=>  false
    str1 === /^[\d]+(\.[\d]+){0,1}$/ #=> false
    str2 === /^[\d]+(\.[\d]+){0,1}$/ #=> false

Also I found alternate way to do this by using match.

Can anyone explain what is (===) operator doing here? How it works? Is there any other alternate way?

http://stackoverflow.com/questions/3025838/what-is-the-operator-in-ruby — rjz, Sep 05 '12 at 08:02

score 3 · Accepted Answer · answered Sep 05 '12 at 08:02

In Ruby, operator overloading can be used to define what each operator does, but it must be done by the class on the left hand side of the operator.

This method is defined in the Ruby Standard Library for the Regexp object class. Reference: http://www.ruby-doc.org/core-1.9.3/Regexp.html#method-i-3D-3D-3D.

It only works with the Regexp class (that is the pattern) on the left hand side because it is defined to work that way only in the Regexp class.

In this case, Regexp defines === as a synonym for =~, which matches a string given a regular expression pattern.

The String class defines the === operator as an equality operator. This means it returns false if the right hand argument is not a string, and otherwise returns true only if both strings match. Reference: http://www.ruby-doc.org/core-1.9.3/String.html#method-i-3D-3D-3D

Is this feature belongs to only 1.9.2??? I am using ruby enterprise edition 1.8.7 , it is working in that. — Rahul Tapali, Sep 05 '12 at 08:45
You'll have to check the documentation for 1.8.7, but many things generally stay the same. — ronalchn, Sep 05 '12 at 08:53

score 1 · Answer 2 · answered Sep 05 '12 at 08:02

1

def is_numeric?(str)
  str =~ /^[\d]+(\.[\d]+){0,1}$/
end

answered Sep 05 '12 at 08:02

Erez Rabih

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RoR: checking for numeric value

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