A free library for iOS for making apps that download images or other data from URLs. Includes caching, easy memory management, etc.

Here we look at how to use @2x graphics file to draw for the iPhone 4 high resolution retina display, explore how to use the new scale property to determine at run time which resolution to use, and how this works for an iPhone app running on the iPad.

How to debug memory crashes in your iPhone app using Instruments and NSZombie. If your app is crashing with ‘BAD ACCESS’ its because your retains and releases are screwed up and you are calling a method on an object you already deleted. This is the easiest technique to figure the problem out.

If an exception is thrown when debugging an iPhone app, without your own exception handling code, that exception won’t stop the debugger until the call stack has totally unwound. On that journey through the call stack it gets caught and disguarded in the event loop. That’s a bummer because then the debugger can’t show you [...]

This article is a screen cast video of my tutorial for beginner iPhone programmers, it’s about the basics of memory management in Objective-C. Memory management is a tough nut for the beginner to crack, particularly in Objective-C and Cocoa for iPhone. Check out my iPhone memory management reading list for more voices on memory management. [...]

Custom UIs on the iPhone are made from UIView containing subviews, I ran across a problem where the subviews were being draw with an annoying blur. Here’s what was happening and how to fix it…

iPhone’s cocoa touch doesn’t seem to have a call to get pixel color from the screen or an image, which I needed to make a simple image based color picker. Here’s a solution to do this using an offscreen graphics context we can use to get pixel by pixel data from the image. I’ve wrapped up the technique in a new class ColorPickerImageView and there’s a complete demo XCode project you can download to see it in action.