我在我的核心数据模型中拥有一对多关系。一餐可以有多种食物。我想用一顿饭中的食物填充一张桌子。所以如果第一餐含有苹果,橙子和柠檬,那么这张桌子就包含了这三种食物。核心数据一对多关系
任何帮助非常感谢,因为我完全卡住了。
这里是我的模型:
而且NSManagedObject类:
Meal.h
@class Food;
@interface Meal : NSManagedObject
@property (nonatomic, retain) NSString *name;
@property (nonatomic, retain) NSSet *foods;
@end
@interface Meal (CoreDataGeneratedAccessors)
- (void)addFoodsObject:(Food *)value;
- (void)removeFoodsObject:(Food *)value;
- (void)addFoods:(NSSet *)values;
- (void)removeFoods:(NSSet *)values;
@end
Food.h
@class Meal;
@interface Food : NSManagedObject
@property (nonatomic, retain) NSString * name;
@property (nonatomic, retain) Meal *meals;
@end
这里是我试图尝试这个,但我有一些问题的代码。
- (NSFetchedResultsController *)fetchedResultsController
{
if (_fetchedResultsController != nil)
return _fetchedResultsController;
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
NSEntityDescription *entity = [NSEntityDescription entityForName:@"Food" inManagedObjectContext:_context];
[fetchRequest setEntity:entity];
[fetchRequest setPredicate:[NSPredicate predicateWithFormat:@"Meal.foods == %@", entity]];
NSSortDescriptor *sort = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:NO];
[fetchRequest setSortDescriptors:[NSArray arrayWithObject:sort]];
[fetchRequest setFetchBatchSize:20];
NSFetchedResultsController *theFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:_context sectionNameKeyPath:nil cacheName:@"Root"];
self.fetchedResultsController = theFetchedResultsController;
_fetchedResultsController.delegate = self;
[fetchRequest release];
[theFetchedResultsController release];
return _fetchedResultsController;
}
你在卡住?请告诉我们你的问题到底是什么。 – sosborn 2012-03-14 02:58:38
为什么在这里使用一对多的关系?如果“食物”代表一种食物而不是特定的食物,那么我希望给定的“食物”实例能够与多餐相关。 – Caleb 2012-03-14 06:21:56
你的问题解决了? – 2012-03-14 06:40:05