标识在CoreData保存之前哪些字段已更改 [英] Identifying which fields have changed before CoreData saves

问题描述

//设置通知

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

//

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

是否还有从updatedObjects确定哪些字段实际改变了？

Is there anyway to determine from the updatedObjects which fields were actually changed?

感谢，
Michael

thanks, Michael

推荐答案

需要使用NSManagedObjectContextWillSaveNotification，并通过用于保存对象的同一NSManagedObjectContext访问您更新的对象。

The following should do the trick, but you will need to use NSManagedObjectContextWillSaveNotification and access your updated objects through the same NSManagedObjectContext used to save the objects.

for(NSManagedObject *obj in updatedObjects){

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

}

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