title: Update attribute in Core Data
body: <p>I know that this has been answered many times but I can't seem to get mine to work.</p>
  
  <p>I have an entity called <code>SchoolName</code>s and this has a single attribute called <code>nameOfSchool</code>. I want to be able to update this attribute.</p>
  
  <pre><code>NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"SchoolName"];
  fetchRequest.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"NameOfSchool" ascending:YES]];
  NSError *errorLoading = nil;
  self.schoolNames = [context executeFetchRequest:fetchRequest error:&amp;errorLoading];
  
  NSLog(@"%d", self.schoolNames.count );
  </code></pre>
  
  <p>I can see in the <code>NSLog</code> that I am loading my data into the <code>schoolNames</code> array. But I have no idea how to update an entry in the array and then save that back to the entity. </p>
  
  <p>Any help much appreciated.</p>