Kirbybase Hacks NilClass

[Daniel Berger]

Ooops, before someone hits me, I made a mistake in the above NULL or
FALSE is NULL not FALSE.
--Apple-Mail-20-8862340--

If only we had a Boolean class we could subclass and/or override.

Oops, that was proposed and shot down.

Dan

 

[James Edward Gray II]

select { |r| r.speed > 300 or r.range < 900 or r.service_date <
Date.today rescue false }

I realized, after I sent that, that my solution is *not* equivalent.
Guess that's a good argument for your way of doing things Jamey.

James Edward Gray II

 

[Jamey Cribbs]

# :title: NullClass
#
# NullClass is essentially NilClass but it differs in one
# important way. When a method is called against it that it
# deoesn't have, it will simply return null value rather then
# raise an error.

class NullClass #< NilClass
class << self
def new
@null ||= NullClass.allocate
end
end
def inspect ; 'null' ; end
def nil? ; true ; end
def null? ; true ; end
def [](key); nil; end
def method_missing(sym, *args)
return nil if sym.to_s[-1,1] == '?'
self
end
end

module Kernel
def null
NullClass.new
end
end

class Object
def null?
false
end
end

Thanks, Trans! I really like this. It makes sense to just create one
null object, like nil does.

Jamey

 

[Jamey Cribbs]

I realized, after I sent that, that my solution is *not* equivalent.
Guess that's a good argument for your way of doing things Jamey.

Well, I just wanted to thank you for starting this whole discussion. I
*really* like getting feedback on KirbyBase and your post has resulted
in some great ideas from people concerning this nil issue.

Bottom line is that I'm going to work on finding a way to satisfy your
request to not override NilClass#method_missing while keeping the
simplicity of KirbyBase's query expressions.

Thanks again for bringing this up.

Jamey

 

[E. Saynatkari]

Well, I just wanted to thank you for starting this whole discussion. I
*really* like getting feedback on KirbyBase and your post has resulted
in some great ideas from people concerning this nil issue.

Bottom line is that I'm going to work on finding a way to satisfy your
request to not override NilClass#method_missing while keeping the
simplicity of KirbyBase's query expressions.

I may be jumping in the deep dark waters of overengineering,
but how about just proxying the call? Instead of:

r.speed # => 3

You would have

r.speed # <#KBDBField:0x...>
r.speed.value # 3
r.speed + 1 # 4

The KBDBField (it is just fun to say fast) proxies all of
its requests to the value object unless said object is nil.

Alternatively, NULL = NullClass.new is not a terrible idea

Thanks again for bringing this up.

Jamey

E

 

[Chris Anderson]

class NullClass #< NilClass

Thanks Trans! I wrote a little module from this called HungryNil, that
you can use to selectively turn nill values into nulls, in a method
chain.

eg:

nil.n #=> null

2.358.n #=> 5

nil.round #=> method missing error

nil.n.round #=> null

2.358.n.round #=> 2

 

[Chris Anderson]

nil.n #=> null

2.358.n #=> 5

nil.round #=> method missing error

nil.n.round #=> null

2.358.n.round #=> 2

sorry, I forgot the link: <a
href="http://jchris.mfdz.com/articles/2006/03/17/hungrynil">HungryNil</a>

 

[Chris Anderson]

this is getting old:
http://jchris.mfdz.com/articles/2006/03/17/hungrynil