Re: flyweight object equivalence
Risking to confuse you even more, you seem to want unique
naming of your objects, so as all flyweights share the same name.
COM's naming mechanism is called monikers. In your case
you'd implement a moniker whose IsEqual method does the
job. You return the moniker from your flyweight initialized with
whatever unique identifier you associate with your internal object.
Thus all flyweights will return monikers initialized with the same
identifier so their IsEqual implementation would do matching.
You can use their GetDisplayName method for obtaining the
ID string when implementing IsEqual. The moniker in this case
is just another flyweight for your object - one that can name the
object. If you want to be more sophisticated, you can have the
moniker return a new flyweight for your object from its
BindToObject method (this would make it a true moniker).
--
=====================================
Alexander Nickolov
Microsoft MVP [VC], MCSD
email: agnickolov@mvps.org
MVP VC FAQ: http://vcfaq.mvps.org
=====================================
"Jason S" <jmsachs@gmail.com> wrote in message
news:1176996505.856150.62500@y80g2000hsf.googlegroups.com...
Hmm. Some really good suggestions here, I'll have to try them soon...
(wish I had more time to investigate this stuff to understand it
fully :( )
Just to clarify my desired behavior, here's a quick example.
W1 -> X <- W2
W3 -> Y <- W4
Two COM flyweights W1 and W2 both point to the same internal (C++-
land) object X. Another two COM flyweights W3 and W4 both point to
internal object Y.
If I want to compare the COM flyweights for true equality (same COM
object), I could do so by querying them for their IUnknown * pointers.
In this case, all 4 of them will be different since they are different
objects.
What I would like to do is design a method that clients can use to
verify whether W1 and W2 both point to the same internal thing. (e.g.
pW1->Equals(pW2)) It should return true for W1 == W2, and W3 == W4,
but false for any other combination of the flyweights. I want this to
work the same whether the interface pointers in question point
directly to the COM objects or whether they point to a proxy.
==
In my specific case, I have a client with an array of interface
pointers, and when it receives a new interface pointer, I would like
to be able to add the new interface pointer only if the underlying
object is the same. My client does not have or want access to the
underlying object itself, but it just wants to be sure to keep
pointers to "unique" (from the standpoint of underlying object
equivalence) flyweights.