NSPredicate用於檢測的屬性的類

我有事件，每個事件具有NSManagedObject娛樂對一的關係，及娛樂具有一對多的關係，並且具有事件的NSSetNSPredicate用於檢測的屬性的類

@interface Event : NSManagedObject 
@property (nonatomic, retain) NSDate *creationDate; 
@property (nonatomic, retain) NSDate * date; 
@property (nonatomic, retain) NSString * objectId; 
@property (nonatomic, retain) NSString * price; 
@property (nonatomic, retain) Entertainment *entertainment; 
@property (nonatomic, retain) Place *place; 
@property (nonatomic, retain) NSString *townName; 
- (void)fillProperties:(NSDictionary *)JSON; 
@end 

@interface Entertainment : NSManagedObject 
@property (nonatomic, retain) NSString * additionalInfo; 
@property (nonatomic, retain) NSNumber * allCommentsLoaded; 
@property (nonatomic, retain) id image; 
@property (nonatomic, retain) NSString * imageURL; 
@property (nonatomic, retain) NSString * info; 
@property (nonatomic, retain) NSString * name; 
@property (nonatomic, retain) NSString * objectId; 
@property (nonatomic, retain) NSSet *comments; 
@property (nonatomic, retain) NSSet *events; 
- (void)fillProperties:(NSDictionary *)JSON; 
@end

娛樂有許多亞類所以，我需要爲讓活動創造這樣NSFetchedResultController，具有特定類

我試圖使用

- (NSFetchedResultsController *)fetchedResultsControllerForEventsFromEntertainment:(Class)className 
{ 
    NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:NSStringFromClass([Event class])]; 
    fetchRequest.predicate = [NSPredicate predicateWithFormat:@"entertainment isMemberOfClass: %@", [className class]]; 
    NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"objectId" ascending:YES]; 
    fetchRequest.sortDescriptors = @[sortDescriptor]; 
    fetchRequest.fetchBatchSize = 20; 
    NSFetchedResultsController *fetchResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil cacheName:nil]; 
    return fetchResultsController; 
}

的娛樂

但我得到的錯誤：

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', 
reason: 'Unknown/unsupported comparison predicate operator type' 
***

我讀到，當我們使用SQLite的工作，這種方法isMemberOfClass不行的，因爲SQLite的不知道這樣的方法。在通常的NSPredicate中，例如簡單數組，它必須工作。

那麼如何從SQLite中獲取具有特定類娛樂的事件？

來源

2013-10-10 MaximusAlarmus

的可能的複製[NSPredicate過濾掉子結果（https：//開頭stackoverflow.com/questions/16636338/nspredicate-that-filters-out-subclass-results） –

在謂詞 a（基於SQLite的）核心數據提取請求中，不可能引用實體名稱或類名稱。

但獲取獲取請求指定的實體的唯一對象，而不是對象的任何子實體，只需設置

[fetchRequest setIncludesSubentities:NO];

來源

2013-10-10 07:32:42

NSPredicate用於檢測的屬性的類

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