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POTransient attributes and FetchRequest?
 

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  1. POTransient attributes and FetchRequest?
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    <p>I have a transient attribute <code>titleFirstLetter</code> in the Book Entity:</p> <pre><code>- (NSString *)titleFirstLetter { NSString *tmpValue = nil; [self willAccessValueForKey:@"titleFirstLetter"]; if ([[self title] length] &gt; 0) { tmpValue = [[[self title] substringToIndex:1] uppercaseString]; if ([[NSScanner scannerWithString:tmpValue] scanInt:NULL]) { //return # if its a number tmpValue = @"#"; } } else { //sanity in case the attribute is not set. tmpValue = @""; } [self didAccessValueForKey:@"titleFirstLetter"]; return tmpValue; } </code></pre> <p>and I am trying to use this attribute as Section name but when I execute:</p> <pre><code> // Create the sort descriptors array. NSSortDescriptor *authorDescriptor = [[NSSortDescriptor alloc] initWithKey:@"titleFirstLetter" ascending:YES]; NSSortDescriptor *titleDescriptor = [[NSSortDescriptor alloc] initWithKey:@"title" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:authorDescriptor, titleDescriptor, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; // Create and initialize the fetch results controller. NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:@"titleFirstLetter" cacheName:nil]; self.fetchedResultsController = aFetchedResultsController; fetchedResultsController.delegate = self; </code></pre> <p>I get this error:</p> <pre><code>*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'keypath titleFirstLetter not found in entity &lt;NSSQLEntity Book id=1&gt;' </code></pre> <p>please help!</p>
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    1. USMarta V.
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    1. COlook at http://stackoverflow.com/a/3553471
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