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我在导航层次结构中有2个级别的UITableViews
。第一页是UITableView
,它使用NSFetchedResultsController
显示Equipment
的所有实例,这很好。在第二页上,我想要取回所有Note
实体的特定片段Equipment
,以便我可以在tableView
中显示它们。如何为CoreData对多关系编写NSPredicate
如何编写NSPredicate
以仅返回相关备注?
- (NSFetchedResultsController *)fetchedResultsController {
if (_fetchedResultsController != nil) {
return _fetchedResultsController;
}
//Init Fetch Request
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
//Entity the NSFetchedResultsController will be managing
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Note"
inManagedObjectContext:self.myContext];
[fetchRequest setEntity:entity];
//Sort Descriptors
NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"noteTime"
ascending:YES];//Primary Sort
NSSortDescriptor *sortDescriptor2 = [[NSSortDescriptor alloc] initWithKey:@"noteText"
ascending:YES];//Secondary Sort
NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1,
sortDescriptor2,
nil];
//Set Sort Descriptors
[fetchRequest setSortDescriptors:sortDescriptors];
// limit Fetch to notes that belong to myEquipment
//self
// NSPredicate *predicate = [NSPredicate predicateWithFormat:[NSString stringWithFormat:@"item.name like '%@'", self.item.name]];
NSPredicate *predicate = [NSPredicate predicateWithFormat:PREDICATE GOES HERE];
[fetchRequest setPredicate:predicate];
[fetchRequest setFetchBatchSize:10];
NSFetchedResultsController *frc = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest
managedObjectContext:self.myContext
sectionNameKeyPath:nil
cacheName:@"Equipment"];
//Set the Delegate Property
frc.delegate = self;
_fetchedResultsController = frc;
//Release Local Memory
[sortDescriptor1 release];
[sortDescriptor2 release];
[sortDescriptors release];
[fetchRequest release];
return _fetchedResultsController;
}
这是否导致了逻辑假读取请求? 查询会是(设备== <设备:0x00000000>(实体:设备...) – ebi 2014-06-25 19:24:36