From: Walton Hoops <walton@...>
Date: 2009-12-08T06:53:32+09:00
Subject: Re: how to check if operation returns an error

> -----Original Message-----
> From: pstoica@gmail.com [mailto:pstoica@gmail.com]
> 
> Hi all, I started learning ruby two weeks ago and I'm loving it. I'm
> coding some date/time program to practice at the moment and I hit a
> wall. I need a way to ask ruby whether or not a certain operation will
> return an error. (I've tried google, I've searched this forum, the
> manuals and IRC but to no avail, so I'm turning to you guys)
> 
> I don't think the code is necessary since it's probably a really easy
> thing such as ".isitanerror" or whatever but here it is anyway.
> 
> To put you in context, before this, the program checks that all the
> input was integers and well formated and then inputs the whole thing
> into an array called "thedate". Now I want to check if the array of
> integers is a date or not (i.e. if someone enters '99' in the 'hour'
> slot I want the program to know it's not correct.) When I enter a real
> date it works, when I enter malformated gibberish the code before
> catches it but if I enter well formated "not date" numbers, the last
> line before the "end" returns an error - so again, what I want to do is
> to test wether or not that last line will return an error without
> running it and breaking the program.

You can't.  You can, however, catch the error when it occurs:

irb(main):006:0> begin
irb(main):007:1*   DateTime.parse 'blah'
irb(main):008:1> rescue
irb(main):009:1>   puts 'learn to write a date fool!'
irb(main):010:1> end
learn to write a date fool!
=> nil
irb(main):011:0>

Have a look at the exceptions section here:
http://www.troubleshooters.com/codecorn/ruby/basictutorial.htm#_Exceptions



> if problems != true
>   dateformated   = thedate[0].to_s + '-' + thedate[1].to_s + '-' +
> thedate[2].to_s + 'T' + thedate[3].to_s + ':' + thedate[4].to_s + ':' +
> thedate[5].to_s
> 
> birthindate   = DateTime.parse(dateformated)
> end
> --
> Posted via http://www.ruby-forum.com/.