Sunday, February 9, 2003

Sometimes I am so stupid it's appalling - using CFNetwork and CFReadStreams Has it really been 8 days since I posted last time? I've been trying to decipher how to use the CFNetwork framework and wrap it in a nice library so that I can do nice and friendly conditional HTTP/1.1 fetches from web servers. The short version of this story is that Java has made me into a moron as far as programming is concerned. Well, that and Apple needs to fix some of their documentation. To get CFNetwork to handle event driven reads from a CFStream, you create a class that opens all of the necessary CFStreams, then you set a context which contains an 'info' pointer (of type void*) which points back at your object. The documentation that Apple provides is a little misleading - it seems to indicate that your entire context datastructure is passed back in the callback: clientCallBackInfo A pointer to context information that was provided when the application previously called CFReadStreamSetClient. That is wrong. What you really wanted to look at is this: clientCallBackInfo The info member of the CFStreamClientContext structure that was used when setting the client for stream. I got screwed for a day because I kept casting the void* pointer to CFStreamClientContext. Grabbing 'info' from that pointer happened to give me the first attribute of my Objective-C object. Points for Java on this one - I'd get a ClassCastException, whereas here all I got was some weird data that I couldn't figure out. Blech... Kudos to Matt Jarjoura for setting up a CFNetwork wiki with some simple example code for using CFNetwork in Cocoa. 4:10:52 AM

© Copyright 2003 Victor Ng.