From: William James <w_a_x_man@...>
Date: 2007-01-14T13:35:18+09:00
Subject: Re: checking if a string matches a regexp - am I missing something?

Rob Sanheim wrote:
> On 1/13/07, James Edward Gray II <james@grayproductions.net> wrote:
> > On Jan 13, 2007, at 9:43 PM, Rob Sanheim wrote:
> >
> > > I figure that I must be missing something really obvious with this
> > > question.  But here goes:
> > >
> > > I want to know if a string matches a regular expression.  I don't care
> > > where the match begins, I don't want a matchdata object, I don't want
> > > to check for nil, I just want a boolean indicating if a string matches
> > > a regexp.  And I want this to be one method call.  From what I can
> > > tell, this is the closest I can get:
> > >
> > > ("string" =~ reg) >= 0 # ugly
> >
> > Just drop the noise:
> >
> > "string" =~ reg # => int results are +true+ and nil is +false+
> >
> > Hope that helps.
> >
>
> True...but here is a cleaned up version of the place where I tried to do that:
>
>  def valid_query?
>  # query is a string accessor
>     if query_is_plain_text?
>       is_valid = valid_query_length? && (query =~ regex)
>     else
>       is_valid = query_is_url?
>     end
>     is_valid
>   end
>
> So of course, when it was both a valid query and had a valid length,
> it would return zero because it matched the start of the regexp.  The
> caller of the method wanted true or false only, not zero.

Who wrote a caller that wanted true or false only, and why?
What does the caller do when it receives 0?

irb(main):002:0> puts 'yeah' if true
yeah
=> nil
irb(main):003:0> puts 'yeah' if 0
yeah
=> nil
irb(main):004:0> puts 'yeah' if false
=> nil

If you actually have a caller written so mindlessly that it
only works with true or false:

    !!(is_valid = valid_query_length? && (query =~ regex) )