Nil associations/embeds/links evaluate as true in some contexts

[IdahoEv]

If i embed or link another object, and the associated object is nil, the association method evaluates as 'true'. This means you have to explictly call .nil?() on an association to see if the object exists or not.

Since this is not at all how Ruby programmers expect nil to behave, it can result in some extremely confusing debugging situations ... if .nil? works, but unless does not. ||= does not work, etc.

---

class MyModel
include Ripple::Document
one :foo, :class_name => "EmbeddedModel"

property :name, String
end

class EmbeddedModel
include Ripple::EmbeddedDocument

property :awesomeness, Integer
end

$ rails console
Loading development environment (Rails 3.1.3)
ruby-1.9.2-p290 :001 > mm = MyModel.new
=> <MyModel:[new] name=nil>
ruby-1.9.2-p290 :002 > mm.foo
=> nil
ruby-1.9.2-p290 :003 > print "no foo" if mm.foo.nil?
no foo => nil
ruby-1.9.2-p290 :004 > print "no foo" unless mm.foo
=> nil
ruby-1.9.2-p290 :005 > mm.foo ||= EmbeddedModel.new(:awesomeness => 100)
=> nil
ruby-1.9.2-p290 :006 > mm.foo
=> nil
ruby-1.9.2-p290 :007 > mm.foo = EmbeddedModel.new(:awesomeness => 100)
=>
ruby-1.9.2-p290 :008 > mm.foo
=>
ruby-1.9.2-p290 :009 > mm = MyModel.new
=> <MyModel:[new] name=nil>
ruby-1.9.2-p290 :010 > mm.foo.class
=> NilClass
ruby-1.9.2-p290 :011 > mm.foo == nil
=> true
ruby-1.9.2-p290 :012 > print "nil" unless nil
nil => nil
ruby-1.9.2-p290 :013 > print "it's nil" unless nil
it's nil => nil
ruby-1.9.2-p290 :014 > print "it's nil" unless mm.foo
=> nil
ruby-1.9.2-p290 :015 > mm.foo.nil?
=> true
ruby-1.9.2-p290 :016 >

[IdahoEv]

version tested was current head: f28a4b9

[IdahoEv]

I've bolded the places where the output is unexpected, in the console log.

[myronmarston]

This is a duplicate of #197.