重置托管对象上下文不起作用
我在 UI 线程中有一个主托管对象上下文 (MOC)，通常由工作线程更新。效果很好！
但是，我有一个视图，在 UI 线程中创建另一个 MOC（称为 EditingMOC）。我通过editingMOC中的objectID读取了myObject。然后，我在 editoringMOC 中对对象 myObject 进行了一些修改。如果用户点击 cancel，则会发生以下情况：
[self.editingMOC reset];
myObjectEdit = [self.editingMOC existingObjectWithID:myObject.objectID error:NULL];
难道不应该将 myObjectEdit 恢复到之前的状态吗？我没有调用保存。尽管如此，myObjectEdit 仍然有我的更改。知道可能出了什么问题吗？
谢谢你！
更新：
显然 myObjectEdit 的刷新是正确的（感谢 Mark Adams）。我追踪到了这个奇怪的行为：
// RESET VALUE - OK
NSLog(@"%@", myEditObject);
self.tableView.userInteractionEnabled = NO;
// OLD VALUE AGAIN - WRONG
NSLog(@"%@", myEditObject);
我没有改变任何与userInteractionEnabled有关的内容。此方法是否有文档中未说明的任何副作用？
I have a main managed object context (MOC) in the UI thread which is usually updated by worker threads. Works fine!
However, I have one view where I create another MOC (called editingMOC) in the UI thread. I read myObject via objectID in editingMOC. Afterwards I do some modifications on the object myObject in the editingMOC. If the user hits cancel, the following happens:
[self.editingMOC reset];
myObjectEdit = [self.editingMOC existingObjectWithID:myObject.objectID error:NULL];
Shouldn't that restore myObjectEdit to it's state as it was before? I did not call save. Nevertheless myObjectEdit has still my changes. Any idea what might be wrong?
Thank you!
Update:
Apparently the refresh of myObjectEdit is correct (Thanks Mark Adams). I tracked it down to this weird behaivor:
// RESET VALUE - OK
NSLog(@"%@", myEditObject);
self.tableView.userInteractionEnabled = NO;
// OLD VALUE AGAIN - WRONG
NSLog(@"%@", myEditObject);
I haven't changed anything regarding to userInteractionEnabled. Does this method have any side effects not stated in the docs?
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您需要将
-refreshObject:mergeChanges:发送到您的NSManagedObjectContext。传入您的NSManagedObject子类并将NO传递给mergeChanges:。这会将对象恢复为故障，并丢弃自上次从持久存储中获取以来的任何更改。在这种情况下，该对象从未进入过存储，因此它被完全丢弃。NSManagedObjectContext 类参考 -
refreshObject:mergeChanges:编辑：从你的问题来看，你可能在线程之间传递对象。在这种情况下，请确保通过 objectID 创建对象，而不是跨线程引用该对象。我假设你已经知道这一点了...
You need to send
-refreshObject:mergeChanges:to yourNSManagedObjectContext. Pass in yourNSManagedObjectsubclass and passNOtomergeChanges:. This turns the object back into a fault and discards any changes since it was last fetched from a persistent store. In this case, the object has never been in a store, so it is completely discarded.NSManagedObjectContext Class Reference -
refreshObject:mergeChanges:Edit: It seems from your question that you may be passing objects around between threads. In that case, be sure to create the object by objectID instead of referencing the object across threads. I'm assuming you already know this though...