Re: Big picture relationships between NSConnection, NSInputStream, NSOutputStream etc
Re: Big picture relationships between NSConnection, NSInputStream, NSOutputStream etc
- Subject: Re: Big picture relationships between NSConnection, NSInputStream, NSOutputStream etc
- From: John Pannell <email@hidden>
- Date: Wed, 3 Dec 2008 20:54:51 -0700
Hi Ken-
I have spent a lot of time in those docs :-) In a nutshell, here's
how I see NSConnection and DO... properly set up, NSConnections on the
server and client side can enable you to pretty much ignore the fact
that two objects live in separate processes. You'll just use regular
obj-c messaging between them. On the server side, you get a
connection, assign it a root object, and "advertise" its presence:
NSConnection *theConnection = [NSConnection defaultConnection];
[theConnection setRootObject:myServerController];
if(![theConnection registerName:@"myServerName"]){
// undesirable, but unlikely
}
On the client side, you need to grab the server-side object (the
"vended" object in the docs) like so...
id myServerObject = [[NSConnection
rootProxyForConnectionWithRegisteredName:@"myServerName host:nil]
retain];
You might typically specify a communications protocol to use (an obj-c
protocol that you create defining the messages that the server object
understands), and also message the server with a reference to self
(the client object) so the server can hang on to a reference to it...
[(NSDistantObject *)myServerObject
setProtocolForProxy:@protocol(myServerProtocol)];
[myServerObject setClientObject:self];
(Note that "setClientObject" is something you implement yourself, can
be named as desired, and its function is to retain a reference to the
client object). Now the server can send regular objective-c messages
to the client object, and the client can send regular objective-c
messages to the server object. Both objects are represented by a
stand-in instance of NSDistantObject in each other's address spaces.
Using NSConnection as above, you really don't need any of the other
classes you mentioned.
Some caveats: Distributed Objects is not present in the iPhone OS, and
I have encountered troubles (that did not have workarounds last I
heard) when using DO with garbage collection.
Also to clarify, NSNetService is not directly related to DO, but might
be more familiar to you as Bonjour - it is used to discover other
processes that advertise their presence on the network.
Hope this helps!
John
Positive Spin Media
http://www.positivespinmedia.com
On Dec 3, 2008, at 8:22 PM, Ken Tozier wrote:
Hi
I'm working my way through the "Distributed Objects" documentation
and am confused about when to use NSConnection, NSInputStream,
NSOutputStream etc. The PictureBrowser example project doesn't even
seem to use NSConnection and does its thing just fine. Reading the
NSConnection docs, I notice the conspicuous absence of any method
that actually allows the transfer of messages and data. It just
seems like something that allows you to connect to something ... and
then has not a single method to actually do anything with that
connection.
I looked at several of the example projects but they're all over the
map. Some use CF functions, some use raw BSD sockets, PictureBrowser
uses NSNetService (something not even mentioned in the Distributed
Object docs) So what is the overview of the function and
interrelationships between these different parts and importantly,
what exactly does one do with an NSConnection?
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