nilchecks.rb

# in ruby, nil is an instance of NilClass. we're monkeypatching NilClass at this point, which is a bad idea for a production app. 
# but for this example, it gets the point across and should help you find a solution to what you want... maybe...
class NilClass
  def method_missing(name, *args)
    if respond_to? name
      return name(*args)
    else
      puts "do something about #{name} being nil, here"
      
      # this will forward the call to the original NilClass.method_missing
      # which will raise the standard "undefined method ..." exception
      # commented out for now, to show you can prevent the error
      # super name, *args
    end
  end
end

class X
  attr_accessor :y
end

class Y
  attr_accessor :z
end

class Z
  attr_accessor :foo
end

require 'ostruct'
somex = X.new
somex.y = Y.new
somex.y.z = "this is the value of z in somex.y.z"

anotherx = X.new
anotherx.y = nil

puts somex.y.z
puts anotherx.y.z 
puts anotherx.y.z.a.b.c

# ... there may be a way to do what you want in a more elegant manner. i don't know off-hand, though.
# hope this helps a little, at least.