Bloggin’ West Again

In order to gather more data for my diploma thesis (more on that later) I tried to write a small console application that queries Spotlight. In theory this was easy: The functionality was already provided in Cocoa and a proof of concept using F-Script worked flawlessly, so there shouldn’t be much of a problem hacking it in Python or Objective-C, right?

Maybe in a Side-Effects-Free^TM world, but in here I spent some hours reading and debugging until some nice IRC user politely (no joke intended) told me to think of the run loop.

So, to make a short story short, here are the fragments that finally did the trick for me:

int main(int argc, char *argv[])
{
    NSRunLoop *currentLoop = [NSRunLoop currentRunLoop];

    // Query Spotlight in here 

    // Let it run for a while ... 
    while (mustContinue && [currentLoop runMode:NSDefaultRunLoopMode
           beforeDate:[NSDate dateWithTimeIntervalSinceNow:1]]) {
        // Collect Results
    }
}

In contrast, what does NOT work is:

// Query Spotlight
sleep()
// Collect Results

What put me on the wrong track was that startQuery() returns instantly, so I though “Okay, they must be spawning some new thread in the background and handle the rest, so it doesn’t matter what I do with this thread …”

(*)
Two hours: getting the idea and trying to make it work
Two hours: being curious why it doesn’t work.
Two hours: being depressed that it doesn’t work
Two hours: being outrageously furious that it still doesn’t work
Ten minutes: apathetically accepting that it doesn’t work and probably never will, asking on IRC for help.
After eight hours and twenty minutes: it works.