Question

我正在使用MagicalRecord更好地更改自定义CoreData功能。

我有两个实体：Offer（视频游戏提供）和System（控制台，PC，etx）。商品可以包含一个或多个系统，我从Parse查询中获取所有数据，然后保存所有数据。

我只有8个系统，所以当我的应用程序启动时，我会获取所有这些并保存魔法记录。然后我调用我的方法获取一些提议并将PFObjects从Parse转换为实体。

这就是

+ (void)createOrUpdateOffersWithArray:(NSArray *)objects completion:(void (^)())completion
{
 [MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {

   for (PFObject *object in objects) {

     Offer *offer = [Offer MR_findFirstByAttribute:@"offerId" withValue:object.objectId inContext:localContext];

     if (offer == nil) {
       offer = [Offer MR_createEntityInContext:localContext];
     }

     // Here I set all the offer values (title, date, etc)... 


     NSSet *offerSavedSystems = [offer mutableSetValueForKey:@"systems"];

     if (offerSavedSystems == nil) {
       offerSavedSystems = [[NSMutableSet alloc] init];
     }

     /* This is a set of all the systems related with the offer */
     NSArray *offerSystems = [object objectForKey:@"sistemas"];

     NSMutableSet *updatedSystems = [[NSMutableSet alloc] init];

     /* Here I query one of my System entities for each in the "offerSystems" array */
     for (NSString *systemKey in offerSystems) {
       System *system = [System MR_findFirstByAttribute:@"key" withValue:systemKey inContext:localContext];
       [updatedSystems addObject:system];
     }

     offer.systems = updatedSystems;

  }

 } completion:^(BOOL contextDidSave, NSError *error) {

   /* UI update*/

  }];

}

奇怪的是，这发生在最后一个for循环中。尽管我确信所有8个系统都在我的CoreData模型中，但这一行

System *system = [System MR_findFirstByAttribute:@"key" withValue:systemKey inContext:localContext];

返回

但最奇怪的是在for循环之前使用NSLOG就像这样

  NSLog(@"SYSTEMS %d", [System MR_countOfEntities]);
  NSLog(@"SYSTEMS WITH LOCAL CONTEXT %d", [System MR_countOfEntitiesWithContext:localContext]);

我得到了这个

  SYSTEMS 8
  SYSTEMS WITH LOCAL CONTEXT 0

我的系统以前使用此方法保存

+ (void)initializeSystems
{
  NSArray *systemsKeys = [[self systems] allKeys];

  for (NSString *systemKey in systemsKeys) {

     System *system = [System MR_findFirstByAttribute:@"key" withValue:systemKey];

     if (system == nil) {
       system = [System MR_createEntity];
     }

     [MagicalRecord saveWithBlockAndWait:^(NSManagedObjectContext *localContext) {
        system.key = systemKey;
        system.name = [self literalForSystem:systemKey];
        system.subscribed = [NSNumber numberWithBool:NO];
     }];
   }
 }

我做错了什么？

感谢您的时间

Answer 1

这行代码存在几个可能的问题

System *system = [System MR_findFirstByAttribute:@"key" withValue:systemKey inContext:localContext];

systemKey值在您的所有实体中都不存在。
system.key值未设置（或无）

因此，首先检查 - 获取所有系统实体并记录'key'值。确保您的密钥确实存在。

其次，最好重构代码以保存后台

+ (void)initializeSystemsWithCompletion:(void (^)())completion
{

    [MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {

        NSArray *systemsKeys = [[self systems] allKeys];

        for (NSString *systemKey in systemsKeys) {

            System *system = [System MR_findFirstByAttribute:@"key" withValue:systemKey inContext:localContext];

            if (system == nil) {
                system = [System MR_createEntityInContext:localContext];
            }

                system.key = systemKey;
                system.name = [self literalForSystem:systemKey];
                system.subscribed = [NSNumber numberWithBool:NO];
        }


    } completion:^(BOOL success, NSError *error) {

    }];

}

在MagicalRecord中处理saveWithBlock和关系时出错

1 个答案: