macOS Xcode problem

[RickRandom]

hi all

I'm trying to learn some mac programming so i'm new to this.. I'm following instructions here http://en.wikibooks.org/wiki/Programming_Mac_OS_X_with_Cocoa_for_beginners/Getting_around_in_Xcode_and_Interface_Builder But wasn't long till i had a problem, just my luck.
http://img286.imageshack.us/img286/4785/xcodeerror6th.png
http://img246.imageshack.us/img246/2420/xcodeerror22kj.png

I'm getting these errors when pressing build&go or pretty much doing anything else too. what's this and how can i fix it Version 2.2.1

 

[gekko513]

What's in your /Developer/SDKs folder?

 

[kainjow]

You may have not installed the SDKs when you installed Xcode. You'll probably have to reinstall Xcode again, and make sure you install the SDKs.