在CoreData保存之前确定哪些字段已更改

Question

//设置通知

[[NSNotificationCenter defaultCenter]
 addObserver:self
 selector:@selector(dataChanged:)
 name:NSManagedObjectContextDidSaveNotification
 object:context];    

//后来

- (void)dataChanged:(NSNotification *)notification{
  NSDictionary *info = notification.userInfo;
  NSSet *insertedObjects = [info objectForKey:NSInsertedObjectsKey];
  NSSet *deletedObjects = [info objectForKey:NSDeletedObjectsKey];
  NSSet *updatedObjects = [info objectForKey:NSUpdatedObjectsKey];

无论如何要从updatedObjects确定哪些字段实际更改了？

谢谢,迈克尔

Answer 1

以下应该可以解决这个问题,但是您需要使用NSManagedObjectContextWillSaveNotification并通过用于保存对象的相同NSManagedObjectContext访问更新的对象.

for(NSManagedObject *obj in updatedObjects){

   NSDictionary *changes = [obj changedValues];
   // now process the changes as you need

}

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