我试图从 NSPredicate 获得不同的结果。
我的代码:
NSFetchRequest *request = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Members" inManagedObjectContext:context];
request.entity = entity;
request.sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"city"
ascending:YES
selector:@selector(caseInsensitiveCompare:)]];
request.predicate = [NSPredicate predicateWithFormat:@"memberDeleted == %@", [NSNumber numberWithBool:NO]];
NSDictionary *properties = [entity propertiesByName];
request.propertiesToFetch = [NSArray arrayWithObject:[properties objectForKey:@"city"]];
request.returnsDistinctResults = YES;
request.fetchBatchSize = 20;
NSFetchedResultsController *frc = [[NSFetchedResultsController alloc] initWithFetchRequest:request
managedObjectContext:context
sectionNameKeyPath:nil
cacheName:@"CityCache"];
[request release];
self.fetchedResultsController = frc;
[frc release];
问题是结果多次返回同一个城市。这个实体有很多成员,每个成员都有一个属性“城市”。
我究竟做错了什么?
谢谢,
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