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: Ken Tozier <email@hidden>
- Date: Wed, 3 Dec 2008 23:14:55 -0500
Thanks John. That cleared up a few things.
Ultimately, what I want to do, is talk directly to a MySQL database
without the need for the MySQL libraries. The libraries target
specific processors and OS versions which makes maintenance a royal
pain. I was thinking I could bypass the whole library zoo by doing
something ike the following
#define DEFAULT_MYSQL_PORT_NUMBER 3306
#define DEFAULT_HOST_NAME @"locahost"
NSSocketPort *socket = [[NSSocketPort alloc] initRemoteWithTCPPort:
DEFAULT_MYSQL_PORT_NUMBER host: DEFAULT_HOST_NAME];
NSConnection *connection = [[NSConnection alloc] initWithReceivePort:
nil sendPort: socket];
In tests, this seemed to connect OK, but I take it from your
explanation, that I would need to send objective C messages which MySQ
doesn't grok. In this case, would I need to set up one or both of
NSInputStream, NSOutputStream to send and receive data? Or would I
have to go even lower into BSD socked land (a la PictureBrowser) to do
this sort of thing?
On Dec 3, 2008, at 10:54 PM, John Pannell wrote:
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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