iphone - 将一个对象插入多个关系 - IOS Core Data

Question

我已经看到了有关帮助解释在一对多关系中添加记录的各种答案，但我似乎无法为我的代码弄清楚它的头或尾。

我有一段关系 - 国家有很多县

我正在将县添加到已经存在的国家/地区，但似乎无法获得将县添加到国家/地区关系的方法...

我的代码是:

@class Country, Property;

@interface County : NSManagedObject

@property (nonatomic, retain) NSNumber * id;
@property (nonatomic, retain) NSDate * last_server_update;
@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) Country *country;
@property (nonatomic, retain) NSSet *properties;
@end

@interface County (CoreDataGeneratedAccessors)

- (void)addPropertiesObject:(Property *)value;
- (void)removePropertiesObject:(Property *)value;
- (void)addProperties:(NSSet *)values;
- (void)removeProperties:(NSSet *)values;

@end

国家/地区.h

@class County, Property;

@interface Country : NSManagedObject

@property (nonatomic, retain) NSNumber * id;
@property (nonatomic, retain) NSDate * last_server_update;
@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) NSSet *properties;
@property (nonatomic, retain) County *counties;
@end

@interface Country (CoreDataGeneratedAccessors)

- (void)addPropertiesObject:(Property *)value;
- (void)removePropertiesObject:(Property *)value;
- (void)addProperties:(NSSet *)values;
- (void)removeProperties:(NSSet *)values;

- (void)addCountiesObject:(County *)value;
- (void)removeCountiesObject:(County *)value;
- (void)addCounties:(NSSet *)values;
- (void)removeCounties:(NSSet *)values;

@end

在我的 Controller 中:

Country * newCounty;
newCounty = [County createEntity];

// Get Country
Country * relatedCountry = [Country findFirstByAttribute:@"id" withValue:[county objectForKey:@"country_id"]];
                 
newCounty.id = [county objectForKey:@"id"];
newCounty.name = [county objectForKey:@"name"];
newCounty.country = relatedCountry;  // Does not compile

顺便说一句，我正在使用 MagicalRecord 进行查找

编辑

错误 在“国家/地区”类型的对象上找不到属性“国家/地区”

关系设置为

国家

• 关系:县
• 目的地:县
• 逆向:国家
• 对多关系:已选中

县

• 关系:国家
• 目的地:国家
• 逆:县
• 对多关系:未选中

Answer 1

尝试改变

Country * newCounty;

至

County * newCounty;

;)