From: Robert Klemme <shortcutter@...>
Date: 2007-07-19T21:32:15+09:00
Subject: Re: array sort_by with nil elements

2007/7/19, Stefan Rusterholz <apeiros@gmx.net>:
> Josselin wrote:
> > I am using the sort_by command
> >
> > @buddies = @user.buddies.compact.sort_by {|item| item.send @criteria}
> >
> >
> > problem arise when one criteria like the user.name is nil  the sort
> > crash....  anyway to avoid it
> >
> > thanks a lot for your lights
> >
> > joss
>
> Simply add a default value (best one that gets sorted in the beginning
> or the end)
> @buddies = @user.buddies.compact.sort_by {|item| item.send(@criteria) ||
> default }

This does not work.

irb(main):003:0> [nil].sort_by {|it| it.send(:length) || 0}
NoMethodError: undefined method `length' for nil:NilClass
        from (irb):3:in `send'
        from (irb):3
        from (irb):3:in `sort_by'
        from (irb):3:in `each'
        from (irb):3:in `sort_by'
        from (irb):3
        from :0

You actually need to deal with the exception or test beforehand that
the item responds to the method.

Kind regards

robert