我有这些对象是唯一的,除了两列我用作UITableView中的显示。由于这个原因,UITableView通常会显示重复项。我需要以某种方式过滤掉这些重复项。
在这种情况下,在FetchResult上设置distinctResult将不起作用,因为这限制了NSFetchedResultsController的功能,并且它要求REsultType是NSDictionary而不是托管对象的子类。
有没有人知道如何使用谓词过滤掉这些重复项?请记住,这些对象上的每个字段都是唯一的,除了其中两个。
-(NSFetchedResultsController *) fetchGroupedObjects:(NSString *)entityDescription
sortField:(NSString *)sortField
withPredicate:(NSPredicate *)predicate {
BPRAppDelegate *delegate = (BPRAppDelegate *)[UIApplication sharedApplication].delegate;
NSManagedObjectContext *context = delegate.managedObjectContext;
//NSError *error;
//Fetch the data....
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription
entityForName:entityDescription inManagedObjectContext:context];
[fetchRequest setEntity:entity];
NSSortDescriptor *groupDescription = [[NSSortDescriptor alloc]
initWithKey:GROUP_NAME ascending:YES];
//Sort by Category Name
NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc]
initWithKey:sortField ascending:YES];
NSMutableArray *sorts = [[[NSMutableArray alloc] init] autorelease];
[sorts addObject:sortDescriptor];
[sorts addObject:groupDescription];
[fetchRequest setSortDescriptors:sorts];
//[fetchRequest setResultType:NSDictionaryResultType];
//[fetchRequest setPropertiesToGroupBy:[entity.propertiesByName valueForKey:CONTRACTOR_NAME];
if (predicate != nil)
[fetchRequest setPredicate:predicate];
//NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];
//NSFetchResultsController
[fetchRequest setFetchBatchSize:20];
NSFetchedResultsController *fetchedResultsController =
[[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
managedObjectContext:context sectionNameKeyPath:GROUP_NAME
cacheName:nil]; //Don't use a cache
[fetchRequest release];
[sortDescriptor release];
[groupDescription release];
return fetchedResultsController; //You can't autorelease this thing... the requestor must do that.
}
答案 0 :(得分:0)
虽然设置一个可选的一对一关系可能更容易(例如,“child”),以便你可以使用NSPredicate获取“child == nil”,你当然可以过滤使用[array enumerateObjectsUsingBlock:]
或等价物在纯物镜C中足够容易,并且只根据您的条件将唯一对象添加到结果数组中。