From: Andreas Schwarz <f@...>
Date: 2007-07-18T18:21:38+09:00
Subject: Optional return values

Hi,

I have a few methods that check permissions, e.g.

unless user.can_view?(object)
  puts "go away"
end

What I want do do now is add the possibility to give the caller more
information why the user doesn't have permission. I want to make it
backwards compatible, so returning [false, NotInGroupError(:group =>
'xyz')] is not an option. The only thing I could think of is giving the
function a String or Array that is modified in place:

def can_view?(object, message='')
  if foo.bar
   message.replace('some error message')
   false
  else
    true
  end
end

That's how one would have to do it in C or VHDL. It does seem kinda
un-rubyish though. Is there some obvious way to do this better that I'm
missing?

Thanks
Andreas

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