From: Stefano Crocco <stefano.crocco@...>
Date: 2008-10-01T20:58:11+09:00
Subject: Re: String delete method help

Alle Wednesday 01 October 2008, Keith Johnston ha scritto:
> Hi,
>
> I have a string which hold a URL. I'm trying to use the string .delete
> method to remove the domain from the url but it isn't working as I
> thought it should from the docs.
>
> For example:
>
> string = "http://groups.google.com/group/ruby-talk-google/"
>
> I want to remove the "http://groups.google.com" part of the string, so
> I tried:
>
> string.delete('http', 'com')
>
> thinking this would delete everything between 'http' and 'com' but all
> I get is the entire string without any changes and with no errors.
>
> I'm probably misunderstanding how the delete function works - can
> someone explain?
>
> Thanks,

There are two reasons for which your code doesn't do what you want:
* String#delete is a non-destructive method, that is it doesn't change its   
receiver but creates a new string which is a copy of the receiver, modifies it 
and returns it:

str = "abc"
str1 = str.delete 'a'
puts str
=> "abc"
puts str1
=> "bc"

If you want to modify the string in place, use String#delete!, instead

* String#delete removes from the string the characters which are the 
intersection between its arguments. This means that a) it works character-
wise, so calling str.delete("abc") will delete all 'a', all 'b' and all 'c', 
not just all instances of the substring 'abc'; b) in your case, the two 
strings you pass to delete have no characters in common, so none will be 
removed.

One way to do what you want is to use sub!:

string = "http://groups.google.com/group/ruby-talk-google/"
string.sub!("http://groups.google.com", '')

I hope this helps

Stefano