我有一个托管的Avatar类和一个托管的User类。User类引用了Avatar类:@interfaceUser:RLMObject...@property(nonatomic,retain)Avatar*avatar;...Avatar类如下所示:@interfaceAvatar:RLMObject@property(nonatomic,retain)NSString*urlStr;@property(nonatomic,retain)NSData*imageData;@end@implementationAvatar+(NSString*)primaryKey{return@"ur