ios – 识别在CoreData保存之前哪些字段已更改

//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];

有没有从更新对象确定哪些字段实际上改变？

谢谢,
迈克尔

解决方法

以下应该做的诀窍,但您将需要使用NSManagedObjectContextWillSaveNotification,并通过用于保存对象的相同的NSManagedObjectContext访问更新的对象.

for(NSManagedObject *obj in updatedObjects){

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

}

参见评论中的讨论.