As a way of atoning for the lack of a Friday Q&A today, I'm pleased to introduce PLWeakCompatibility. Do you like ARC? Do you need to support older OS releases? Do you wish you could use __weak variables on those older OSes? If so, then I have good news for you! PLWeakCompatibility is the solution you've been looking for.

I'm extremely excited to announce a new library for Cocoa and Cocoa Touch development: MAZeroingWeakRef. In short, it's a library which allows zeroing weak references to be used in retain/release Cocoa code. This has all sorts of uses and should make retain/release coding less painful. While I discussed this in detail in my Friday Q&A post this week, I also want to make a separate announcement for people who don't want to read through all of the horrible details.

Welcome back to another Friday Q&A. I'm off to C4 today (hope to see you there!) but I've prepared this in advance so everyone stuck at home (or worse, work) can at least have something interesting to read. Over the past four weeks I've introduced Grand Central Dispatch and discussed the various facilities it provides. In Part I I talked about the basics of GCD and how to use dispatch queues. In Part II I discussed how to use GCD to extract more performance from multi-core machines. In Part III I discussed GCD's event dispatching mechanism, and in Part IV I took care of various odds and ends that I hadn't covered before. This week I'm going to examine a practical application of using GCD to speed up the production of thumbnails for a large quantity of images, a topic suggested by Willie Abrams.

Cocoa's Key-Value Observing facilities are extremely powerful and useful. Unfortunately they have a really terrible API that's inherently broken in a couple of different ways. I want to discuss how it's broken, and a way to make it better.