From: Bill Kelly <billk@...>
Date: 2009-09-07T16:57:52+09:00
Subject: Re: Type checking function parameters


From: "Josh Cheek" <josh.cheek@gmail.com>
>
> Personally, I've been wondering what would happen if nil just returned nil
> for every undefined method. Essentially, instead of always having to put
> if x && x.value && x.value > 3
> 
> I could just put
> if x.value > 3
> 
> because if x was nil, then nil.value would be nil, and nil.>(3) would be
> nil.
> 
> I just wonder if this would break things, or is a naive question to ask, so
> I've been a little silent about it. But it keeps coming back to me, because
> a lot of edge case errors revolve around nil not responding to methods.

Can if you want:

irb(main):022:0> class NilClass
irb(main):023:1>   def method_missing(*args)
irb(main):024:2>     nil
irb(main):025:2>   end
irb(main):026:1> end

irb(main):027:0> nil.foo.bar
=> nil
irb(main):028:0> nil > 3
=> nil

etc.

Objective-C works that way.

The downside is, for cases where you are calling a method
on an object you really did not want or expect to be nil,
you no longer get the error at the point of that method
call.  To me having code fail fast in error conditions is
more important, so I don't patch NilClass as shown above.
But, ruby allows it if you really want.


Regards,

Bill