NSFetchResultsController委託不獲取調用

Question

我有以下代碼：

- (NSFetchedResultsController *)fetchedResultsController { 
    // Set up the fetched results controller if needed. 
    if (fetchedResultsController == nil) { 

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; 
     // Edit the entity name as appropriate. 
     NSEntityDescription *entity = [NSEntityDescription entityForName:@"DiskStory" inManagedObjectContext:self.managedObjectContext]; 
     [fetchRequest setEntity:entity]; 

     fetchRequest.predicate = [NSPredicate predicateWithFormat:@"isRemoved == %@", [NSNumber numberWithBool:NO]]; 

     // Edit the sort key as appropriate. 
     NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"created" ascending:NO]; 
     NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; 

     [fetchRequest setSortDescriptors:sortDescriptors]; 

     // Set limit 
     [fetchRequest setFetchBatchSize:25]; 
     // Set batch size 
     [fetchRequest setFetchLimit:50]; 


     NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:kSavedStoryCache]; 
     aFetchedResultsController.delegate = self; 
     fetchedResultsController = aFetchedResultsController; 
} 
    return fetchedResultsController; 
}  

在我viewDidLoad中

我：

NSError *error = nil; 
    if (![[self fetchedResultsController] performFetch:&error]) { 
     NSLog(@"Unresolved error %@, %@", error, [error userInfo]); 
    } 

我想知道爲什麼我的：

- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller { 

} 

委託，ISN不叫？我在裏面放了一個斷點。任何想法？

Answer 1

我想你已經使用了自我。在錯誤的地方。請參閱下面的代碼;我已經添加了註釋的修改

- (NSFetchedResultsController *)fetchedResultsController { 
    // Set up the fetched results controller if needed. 
    if (fetchedResultsController == nil) { 

     NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; 
     // Edit the entity name as appropriate. 
     NSEntityDescription *entity = [NSEntityDescription entityForName:@"DiskStory" inManagedObjectContext:self.managedObjectContext]; 
     [fetchRequest setEntity:entity]; 

     fetchRequest.predicate = [NSPredicate predicateWithFormat:@"isRemoved == %@", [NSNumber numberWithBool:NO]]; 

     // Edit the sort key as appropriate. 
     NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"created" ascending:NO]; 
     NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil]; 

     [fetchRequest setSortDescriptors:sortDescriptors]; 

     // Set limit 
     [fetchRequest setFetchBatchSize:25]; 
     // Set batch size 
     [fetchRequest setFetchLimit:50]; 


     NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:kSavedStoryCache]; 
     aFetchedResultsController.delegate = self; 
     fetchedResultsController = aFetchedResultsController;  // -> Shouldn't be self.fetchedResultsController 
} 
    return fetchedResultsController;  // -> Shouldn't be self.fetchedResultsController 
} 

另外，如果您有合成的fetchedResultsController如下：

fetchedResultsController = _fetchedResultsController 

然後在- (NSFetchedResultsController *)fetchedResultsController方法，你應該把它稱爲_fetchedResultsController

Answer 2

我有此問題之前，它不會在您首次撥打performFetch時調用，但僅當fetchedResultsController中的數據實際發生更改時纔會調用。例如，當您從該提取結果中的上下文中刪除對象時，將調用委託。