Using this line gives warnings in the compiler:
propertyListWithData: expects a NSData object but obviously in the example an NSMutableArray is passed as input:
//pack our todoItems into an NSData object
NSData *data = [NSPropertyListSerialization propertyListWithData:todoItems options:0 format:NSPropertyListXMLFormat_v1_0 error];
Is this something that has changed in the last x-code version?