Your iPhone Development Questions Answered

I’ve been getting a number of questions from programmers about iPhone development.  I thought I would compile the answers into one place and push them out into the world.

The iPhone SDK has been updated at a blistering pace and the documentation has not kept up with the API changes as quick as it could be.  Some of the information from Apple is inconsistent or incomplete.

Why do you have to create a Cocoa Touch application?

It’s not really possible to have command-line applications on the iPhone.  So, you need to have some sort of view that can talk to the window manager on the iPhone.

What’s a XIB file?

XIB stands for XCode Interface Builder.  It is the filetype that is spit out by the Interface Builder application.

http://developer.apple.com/tools/interfacebuilder.html

NIB stands for NextStep Interface Builder.  It is the legacy filetype and name.  Back in the day, when Steve was banished from Apple, he started a company called NeXT.  It was eventually purchased by Apple.  But a ton of work on Mac OS X, Cocoa, Objective-C came from NeXT.

http://en.wikipedia.org/wiki/NeXT

What’s up with all of this Objective-C stuff?

The best cheat sheet I’ve seen for Objective-C is here:

http://developer.apple.com/iphone/gettingstarted/docs/objectivecprimer.action

You need to be logged in as a registered Apple Developer to access that page.

The general rule is that if you see an @ sign, it is a directive to the compiler.  If you see lines of code wrapped in square brackets, [...], then it is a message to a Objective-C object.

What’s a framework?

A framework is kind of like a class library in the Java sense.  Here is the Framework Programming Guide:

http://developer.apple.com/documentation/MacOSX/Conceptual/BPFrameworks/Frameworks.html

Whenever you have a question about a high-level concept, you can search for the accompanying guide here:

http://developer.apple.com/documentation/DeveloperTools/Xcode-date.html 

Why do class names start with ‘NS’?

NS stands for NeXTSTEP.  Objective-C doesn’t have namespaces, so classes in frameworks get prefixes.

Newer frameworks get CF for Core Framework, CA for Core Audio, CM for Core Media, etc.