Cocoa Is My Girlfriend

In my first post I wrote about using NSOperation to grab an image of the current frame of a QuickTime movie while it was playing and save it out to the filesystem. Considering the excitement that is surrounding Core Animation these days, I thought it might be interesting to take that project and change it to instead grab the current frame and animate it across the screen using a Core Animation layer (CALayer). I had to employ a few tricks to get it to work, but the end result, while completely useless, is quite excellent.



 



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Forget Mandelbrot sets (Apple coding headstarts) and Expression Trees. NSOperation is really not that hard.

In his post, Marcus introduced how to use NSOperation to greatly simplify multi-threading tasks in your application. I am now going to provide a step-by-step walk-through sample application that uses NSOperation, NSOperationQueue, and QTKit.

While looking around the Internet, I noticed that the only examples of using NSOperation available were related to scientific applications. I wanted something that I could relate to a little better and since I’ve been working with QTKit a lot lately, I figured it would be a good framework to build from. This application simply grabs images of a movie while it is playing back and saves them out to a file. It’s pretty simple, but it shows how to do something fairly practical. Read more

Threading is hard in any language. And what is worse, when it goes wrong, it usually goes wrong in a very bad way. Because of this, programmers either avoid threading completely (and refer to it as the spawn of the devil) or spend a LOT of time making sure that everything is perfect.

Fortunately, Apple has made a lot of progress in OS X 10.5 Leopard. NSThread itself has received a number of very useful new methods that make threading easier. In addition, they have introduced two new objects: NSOperation and NSOperationQueue. Read more