I have a book about objective-c and one about cocoa programming but I was wondering if these books would be useful anymore as a quick reference? They are from 2002 and 2003 but they are very cheap. Are they outdated?
http://www.amazon.com/gp/product/0596004621/ref=oss_product
http://www.amazon.com/gp/product/0596004230/ref=oss_product
http://www.amazon.com/gp/product/0596004621/ref=oss_product
http://www.amazon.com/gp/product/0596004230/ref=oss_product