The text states to add the following code to initWithFileURL:, however does not specifically state where to insert this code. The file is WeightHistory.m, and the specific location is within the if conditional block, so that initWithFileURL: completed is...

- (id)initWithFileURL:(NSURL *)url
{
self = [super initWithFileURL:url];

if (self)
{
// Set an initial defaults
_weightHistory = [[NSMutableArray alloc] init];

// Monitor document state
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(documentStateChanged:) name:UIDocumentStateChangedNotification object:self];
}

return self;
}