RunLoops, WebServices Framework, and WSMakeStubs

FROM : Joseph Heck
DATE : Tue May 31 05:00:10 2005

I have been spending the weekend disecting code from WSMakeStubs and 
getting into the depths of the WebServices framework, and I'm having 
some trouble understanding a section of code.

When you use WSMakeStubs, it generates a pretty standard template 
object (WSGeneratedObj) which has within it a getResultsDictionary 
method. Prior to it's getting to this method, it's established the 
WSMethodInvocationRef with an asynchronous callback. So far, I'm all 
with this plan of attack. Then we get into this method:

The method in question:

- (NSDictionary*) getResultDictionary
{

    if (fResult == NULL) {
        if (fAsyncTarget != NULL) {
            fAsyncTarget = NULL;
            fAsyncSelector = NULL;
        }

        if (fResult == NULL) {
            WSMethodInvocationRef invocation = [self getRef];
            CFStringRef wsGeneratedMode = CFSTR("NS-WSSYNC");

            WSMethodInvocationScheduleWithRunLoop(invocation, 
CFRunLoopGetCurrent(), wsGeneratedMode);

            while (fResult == NULL)
                CFRunLoopRunInMode(wsGeneratedMode, -1.0, true);

            WSMethodInvocationUnscheduleFromRunLoop(invocation, 
CFRunLoopGetCurrent(), wsGeneratedMode);

        }

        if (fResult == NULL) {
            [self handleError:@"WSMethodInvocationInvoke failed in 
getResultDictionary" errorString:NULL 
errorDomain:kCFStreamErrorDomainMacOSStatus errorNumber:paramErr];
        }
    }
    return fResult;
}

What I don't understand is the call to CFRunLoopRunInMode. The 
documentation on CFRunLoopRunInMode talks about running a runloop for 
0 seconds, and > 0 seconds, but doesn't say anything about < 0 seconds.

Is this method call a mechanism to guarantee that the scheduled 
invocation will get called and when this method returns it will have 
definitively been invoked?

-joe