Several weeks ago I asked for some help understanding DM's
implementation of the Identity Map pattern, but didn't get a response,
unfortunately. I'd like to kindly ask again :)
See, I like DM a lot -- and I'm attempting to use it for persistence
in a MUD I'm writing for fun and experience. Something that's very
important in that kind of environment is that one object only ever
exists to represent one database row, or we end up with things like
two players in "the same room", but the Ruby Player objects are
actually referencing two different Room objects.
With the Identity Map pattern, I thought I wouldn't have this problem
-- I thought that this would be true:
Player.get(1).object_id == Player.get(1).object_id
Not so. I found that I had to do something like this:
repository(:default) do
Player.get(1).object_id == Player.get(1).object_id
end
This works, but I don't think I can use that in any useful way in my
game... I've attempted to read the code and try to figure out why it
works this way, but what would help immensely is a little bit of
narrative about the "why" behind this implementation. I'm guessing it
has something to do with threading but I'm just not experienced enough
to figure it all out on my own.
A "Spotlight On Identity Map" would be awesome, too :) but really I'm
just looking for a quick kick start so that I can wrap my head around
the code and maybe create my own adapter or something that alters this
behavior, if that's even possible.
Thanks!
Brent
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