From: G_ F_ <8si.greg@...>
Date: 2009-09-08T01:56:06+09:00
Subject: Re: Date & time validation

Ne Scripter wrote:
> Just an update of where I am. This is what I have
> 
> if date =~ (/\d{4}\/\d{2}\/\d{2}/)
>   puts date
> else
>   date = (Date.strptime(date, "%Y/%m/%d"))
> end
> 
> This works to an extent but does not deal with a string which contains a 
> valid date but still invalid data like so
> 
> 2009/09/07 12:12:12
> 
> This would be passed as valid when it is not only a string containing 
> yyyy/mm/dd.

Ok, to summarize to see if I've got it right:

     blah 2009/09/07 blah     # <-- is what we want to accept
     blah 2009/09/07 12:00:00 blah # <-- is what we want to reject

%r#\d{4}/\d{2}/\d{2}# matches a date but gives a false positive for 
dates followed by time.

You could filter out lines that have date followed by time using 
something like:

    next if %r#\d{4}/\d{2}/\d{2}\s+\d{2}:\d{2}:\d{2}#

then capture any that make it past that test with a regular date regex.

Or, you can combine the test and capture in one regex pattern using 
look-ahead...

    %r#(\d{4}/\d{2}/\d{2})\s+(?!\d{2}:\d{2}:\d{2})# =~ 'blah 2009/01/01 
blah'  # => 5
    %r#(\d{4}/\d{2}/\d{2})\s+(?!\d{2}:\d{2}:\d{2})# =~ 'blah 2009/01/01 
12:00:00 blah'  # => nil

The first line successfully matches "text date text".
The second line rejects "text date time text".
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