Re: Messaging Passing and context

Wow, phone glitch, sorry.

I was _going_ to say: there is a caller. It tells you the entire stack of
the current method.

In theory it may also be possible to query the ObjectSpace to see what
objects hold a reference to your nerd. However there's no ruby-level
concept for "only one Place can hold a reference to a Person" so to enforce
that rule you'd have to set up either a .location 'property' on person (a
ref back to the Place they're in) or an authoritative person:place map, or
something like that.  But I think that's not what you're asking for.

Sent from my phone, so excuse the typos.
On Apr 7, 2013 12:48 PM, "Julian Leviston" <[e-mail]> wrote:

> Hi,
>
> I've often wanted what I'm about to describe.
>
> Some history about me, so you know this isn't a complete noob question: I
> understand separation of concerns and encapsulation quite well (at least, I
> think I do). I've been programming in object oriented languages for most of
> my life (I'm 37, and I started SmallTalk when I was 17). I've programmed in
> most languages: SmallTalk, Java, Ruby, forth, Python, C/C++, BASIC,
> VisualBasic, ASM, LISP (common, scheme, racket), JavaScript, Self, bit of
> Haskell, Erlang etc., etc.
>
> Context here is object-oriented message sending:
>
> class Person
> attr_accessor :mood
> def say_hi_to(someone)
> puts "hiya"
> end
> end
>
> class Nerd < Person
> # likes inside, dislikes outside
> end
>
> class Jock < Person
> # likes outside, dislikes inside
> end
>
> class Socialite < Person
> # doesn't care in or outside, but only likes places where people are
> interacting socially
> end
>
> class Place
> attr_accessor :inside, :social, :bookish
> def initialize(&block)
> if block
> yield
> end
> end
> end
>
> class Playground < Place
> def intiialize(&block)
> self.inside = false
> self.social = true
> self.bookish = false
> super(&block)
> end
> end
>
> def Library < Place
> def initialize(&block)
> self.inside = true
> self.social = false
> self.bookish = true
> super(&block)
> end
> end
>
> def Field < Place
> def initialize(&block)
> self.inside = false
> self.social = false
> self.bookish = false
> super(&block)
> end
> end
>
> field = Field.new {
> julian = Nerd.new
> dave = Jock.new
> greginsky = Socialite.new
> }
>
> So what I'm interested in, when an object sends a message to another
> object, why is there no context-sensitivity? In other words, (all
> judgements aside as this is just a trivial example), I'd like the nerd to
> be defined as a person who dislikes outside areas, therefore behaves
> according to his mood when he's outside perhaps.
>
> Instantiating a Nerd inside a FIeld... or messaging him with the say_hi
> type message should be able to bear some context on what that nerd's reply
> is. I'm not stipulating a tight coupling of context to object, I *like*
> decoupled contexts, and I like interfaces, but just like the mechanism of
> introspection, it'd be useful and nice to be able to garner *some*
> information about the calling context, especially if (and this is my real
> beef) the calling context WANTS TO GIVE THE INFORMATION. The obvious
> solution is simply to change the interface so it contributes a variable
> which passes across this information, but versioning interfaces is a
> complete pain - I'd like to have a common object (called caller, possibly)
> that I could query from within a method without the caller having to pass
> through "self" every single time. Thus we could then apply some duck typing
> in the callee side and get it to ask some questions of its context before
> responding to messages.
>
> Am I missing some obvious design considerations here?
>
> I guess I'm talking more about language design than language usage, so
> there might be a better place to discuss this. Comments?
>
> Julian
>