From: Eugen Minciu <minciue@...>
Date: 2007-07-20T01:17:31+09:00
Subject: Re: RCR? Added syntax for chains that possibly return nil

Excerpts from Stefan Rusterholz's message of Thu Jul 19 16:31:01 +0300 2007:
> One type of construct in ruby that somewhat annoys me and IMHO reduces
> readability is working around cases where an intermediate method might
> return nil. Those cases are e.g.
> 
> while (line = gets && line.chomp)
> foo = (bar && bar.baz && bar.baz.quuz) || default # bar might be nil, so
> might bar.baz and bar.baz.quuz
> 
> There are some more constructs, most of you surely already used such
> stuff or just spread it onto a bit more of lines.
> While all of this is fine, maybe that could be improved. My RCR would be
> to introduce a new syntax besides . for method invocation, which on the
> first nil aborts any further method calls on it and returns nil.
> 
> E.g. the above examples would become:
> while line = gets->chomp
> foo = bar->baz->quuz || default
> 
> -> was the first best that came to my mind, if you have better ideas,
> please state.
> Unlike e.g. making nil to respond to every method returning self, this
> solution would put the coder in power as to where he cares about getting
> nil (e.g. he wants an exception if foo is nil, so he just writes
> foo.bar, if he doesn't want one, he writes foo->bar) and where he just
> wants to get the nil value back.
> 
> Do you think this RCR is worth to make?
> 
> Regards
> Stefan
> 
how about this ugly creature?

<hack>
class Object
  alias regular_method_missing method_missing
  def method_missing(meth)
    if meth.to_s[0]=='_'[0]
      return nil
    else
      regular_method_missing(meth)
    end
  end
end

puts "yay, it works" unless 3._foo._bar._baz
</hack>

Not exactly like your syntax but gets the job done.

Also, you might want to consider the proper way(tm) of doing it (I think)

<proper way>

begin
  foo.bar.baz.whatever
rescue
  puts "yay it works"
end

</proper way>

Also works as a one liner:
x = begin 3.foo.bar.baz; rescue; nil; end

-- 
Eugen Minciu.

Wasting valuable time since 1985.