I'm trying to build some sample code from an Objective-C book I just got. 

I'm using an older (2006, 32-bit, Snow Leopard) MacBook Pro with Xcode 4.2. I get about 8 errors about "inconsistent number of instance variables specified". 

I compiled the same code on a newer MacBook Pro (2010, 64-bit, Lion) and everything compiles just fine.

Here's a picture with the code and errors expanded:

[![](https://i.stack.imgur.com/mcY23.png)](https://i.stack.imgur.com/mcY23.png)