One of the most common questions from the iPhone workshops we held recently is: “What is key value coding and why the heck am I getting this error?” This error being something like: 2009-07-01 15:50:55.423 AppName[1169:20b] *** Terminating app due to uncaught exception ‘NSUnknownKeyException’, reason: ‘[ setValue:forUndefinedKey:]: this class is …