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iOS Application icons & sizes Here the way :  Below are some useful guidelines for naming & sizing of icon files required for iPhone-only apps, iPad-only apps, and Universal apps. iPhone-only Apps Include the following in your application's Resources group in the Xcode project: Image Size (px) File Name Used For Required Status 512x512 iTunesArtwork Ad Hoc iTunes Optional but recommended 57x57 Icon.png App Store and Home screen on iPhone/iPod touch Required 114x114 Icon@2x.png Home screen for iPhone 4 High Resolution Optional but recommended 72x72 Icon-72.png Home screen for iPad compatibility Optional but recommended 29x29 Icon-Small.png Spotlight and Settings Optional but recommended 50x50 Icon-Small-50.png Spotlight for iPad compatibility Recommended if you have a Settings bundle, otherwise optional but recommended 58x58 Icon-Small@2x.png Spotlight and Settings for iPhone 4 High Resolution ...

Zeroing Weak References in Objective-C by  Mike Ash    It's that time of the biweek again. For this week's Friday Q&A, Mike Shields has suggested that I talk about weak references in Objective-C, and specifically zeroing weak references. I've gone a bit further and actually implemented a class that provides zeroing weak references in Objective-C using manual memory management. Weak References First, what is a weak reference? Simply put, a weak reference is a reference (pointer, in Objective-C land) to an object which does not participate in keeping that object alive. For example, using memory management, this setter creates a weak reference to the new object:     - ( void ) setFoo: ( id )newFoo     {         _foo = newFoo;     } Because the setter does not use  retain , the reference does not keep the new object alive. It will stay ali...