核心数据NSFetchRequest还获取实体的子对象

Question

我是iOS dev和Core Data的新手.我有一个父NSManagedObject

@class Units;
@interface Properties : NSManagedObject

@property (nonatomic, retain) NSString * descr;
@property (nonatomic, retain) NSString * address;
@property (nonatomic, retain) NSString * city;
@property (nonatomic, retain) NSString * state;
@property (nonatomic, retain) NSString *zipCode;
@property (nonatomic, retain) NSString * imageKey;
@property (nonatomic, retain) NSString * numberOfUnit;
@property (nonatomic, retain) NSData * thumbnailData;
@property (nonatomic, strong) UIImage * thumbnail;
@property (nonatomic) double orderingValue;
@property (nonatomic, retain) NSSet *units;

和一个孩子:

@class Properties;

@interface Units : Properties

@property (nonatomic, retain) NSString * unitDescr;
@property (nonatomic) int16_t unitNumber;
@property (nonatomic, retain) Properties *property;

当我使用此方法获取父属性以在tableview中显示父属性对象时:

- (void)loadAllItems
{
    if (!allItems) {
        NSFetchRequest *request = [[NSFetchRequest alloc] init];

        NSEntityDescription *e = [[model entitiesByName] objectForKey:@"Properties"];
        [request setEntity:e];

        NSSortDescriptor *sd = [NSSortDescriptor
                                sortDescriptorWithKey:@"orderingValue"
                                ascending:YES];
        [request setSortDescriptors:[NSArray arrayWithObject:sd]];

        NSError *error;
        NSArray *result = [context executeFetchRequest:request error:&error];
        if (!result) {
            [NSException raise:@"Fetch failed"
                        format:@"Reason: %@", [error localizedDescription]];
        }

        allItems = [[NSMutableArray alloc] initWithArray:result];
    }
}

我遇到了核心数据上下文获取父实体的子对象的问题.我只想返回父对象.

例如,如果我有一个包含3个单位的属性,则属性tableview应该只显示1行,但它显示4行(1个父级和3个子级).

我如何只返回父对象？

谢谢.

Answer 1

看看NSFetchRequest的setIncludesSubentities方法.如果您的数据模型反映了代码中的继承模式,那么如果您正确设置了获取请求,则获取请求将不会获取子实体.

NSFetchRequest *request = [[NSFetchRequest alloc] init]; request.includesSubentities = NO;