Question

我有一个非常简单的模型，有两个对象：名称和类别。一个名称可以在许多类别中（它是单向关系）。我正在尝试使用8个名称创建8个类别。示例代码：

        NSMutableArray *localArray = [NSMutableArray arrayWithObjects:
                                  [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                   @"g1", @"Name",
                                   @"g1", @"Icon",
                                   [NSNumber numberWithBool:YES] , @"Male",
                                   nil],
                                  [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                   @"g2", @"Name",
                                   @"g2", @"Icon",
                                   [NSNumber numberWithBool:YES] , @"Male",
                                   nil],
                                  [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                   @"g3", @"Name",
                                   @"g3", @"Icon",
                                   [NSNumber numberWithBool:YES] , @"Male",
                                   nil],
                                  [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                   @"g4", @"Name",
                                   @"g4", @"Icon",
                                   [NSNumber numberWithBool:YES] , @"Male",
                                   nil],
                                  [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                   @"g5", @"Name",
                                   @"g5", @"Icon",
                                   [NSNumber numberWithBool:YES] , @"Male",
                                   nil],
                                  [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                   @"g6", @"Name",
                                   @"g6", @"Icon",
                                   [NSNumber numberWithBool:YES] , @"Male",
                                   nil],
                                  [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                   @"g7", @"Name",
                                   @"g7", @"Icon",
                                   [NSNumber numberWithBool:YES] , @"Male",
                                   nil],
                                  [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                   @"g8", @"Name",
                                   @"g8", @"Icon",
                                   [NSNumber numberWithBool:YES] , @"Male",
                                   nil],
                                  nil];
    NSMutableArray *localArray2 = [NSMutableArray arrayWithObjects:
                                   [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                    @"Test1", @"Name",
                                    nil],
                                   [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                    @"Test2", @"Name",
                                    nil],
                                   [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                    @"Test3", @"Name",
                                    nil],
                                   [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                    @"Test4", @"Name",
                                    nil],
                                   [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                    @"Test5", @"Name",
                                    nil],
                                   [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                    @"Test6", @"Name",
                                    nil],
                                   [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                    @"Test7", @"Name",
                                    nil],
                                   [NSMutableDictionary dictionaryWithObjectsAndKeys:
                                    @"Test8", @"Name",
                                    nil],
                                   nil];

    NSError *error;
    NSManagedObjectContext *moc = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext];
    for(NSMutableDictionary *item in localArray) {
        NSManagedObject *category = [NSEntityDescription insertNewObjectForEntityForName:@"Category" inManagedObjectContext:managedObjectContext];
        [category setValue:[item objectForKey:@"Name"] forKey:@"Name"];
        [category setValue:[item objectForKey:@"Icon"] forKey:@"Icon"];
        [category setValue:[item objectForKey:@"Male"] forKey:@"Male"];
        for(NSMutableDictionary *item2 in localArray2) {
            NSManagedObject *name = [NSEntityDescription insertNewObjectForEntityForName:@"Name" inManagedObjectContext:managedObjectContext];
            [name setValue:[item2 objectForKey:@"Name"] forKey:@"Name"];
            [[name mutableSetValueForKey:@"CategoryRelationship"] addObject:category];
        }
    }
    [moc save:&error];

这是一个问题 - 我已经检查过保存了8个类别，保存了64个名称，但所有名称中只有8个与任何类别相关联。所以当我在类别中查询姓名时：

[NSPredicate predicateWithFormat:@"CategoryRelationship.@count != 0"]

...有8个元素，当我查询时：

[NSPredicate predicateWithFormat:@"CategoryRelationship.@count = 0"]

......有56个元素。

当我双向建立关系时，它有效。这里有什么？

Answer 1

首先，您的关系应始终是双向的。如果不是，那么您将看到参考完整性和性能方面的问题。

核心数据关系问题

1 个答案: