从一个NSManagedObjectContext保存的更改不反映在主NSManagedObjectContext上

问题描述

我有一个主要的NSManagedObjectContext，它是在appDelegate中创建的。

I have a main NSManagedObjectContext that it's created in the appDelegate.

知道，我使用另一个NSManagedObjectContext来编辑/添加新对象而不影响主NSManagedObjectContext，直到我保存它们。

Know, I'm using another NSManagedObjectContext for editing/adding new objects without affecting the main NSManagedObjectContext, until I save them.

当我保存第二个NSManagedObjectContext时，更改不会反映在主NSManagedObjectContext中，但是如果我从模拟器打开.sqlite数据库，已正确保存到.sqlite数据库中。不管我是否再次获取数据，即使我创建了第三个NSManagedObjectContext，我看不到从第二个NSManagedObjectContext的更改，但这些更改在磁盘上这一刻...

When I save the second NSManagedObjectContext, the changes are not reflected in the main NSManagedObjectContext, but If I open the .sqlite database from simulator, the changes have been saved correctly into the .sqlite database. No matter if I fetch again the data, even if I create a third NSManagedObjectContext, I can't see the changes from the second NSManagedObjectContext, but those changes are on disk at this moment...

如果我退出并打开应用程序，所有更改都在那里。

If I quit and open the app, all changes are there.

什么可能导致主NSManagedObjectContext不能看到商店的新更改？

What can cause the main NSManagedObjectContext not to see the new changes of the store ?

在这种方法之前，我使用了相同的NSManagedObjectContext和undoManager，但我想更改它使用两个不同的NSManagedObjectContext。

Before this approach, I was using the same NSManagedObjectContext and undoManager, but I want to change it to use two different NSManagedObjectContext.

感谢，

m。

second NSManagedObjectContext save:
-----------------------------------------

    NSError* error = nil;

    if ([managedObjectContext hasChanges]) {
        NSLog(@"This new object has changes");
    }

    if (![managedObjectContext save:&error]) {
        NSLog(@"Failed to save to data store: %@", [error localizedDescription]);
        NSArray* detailedErrors = [[error userInfo] objectForKey:NSDetailedErrorsKey];
        if(detailedErrors != nil && [detailedErrors count] > 0) {
            for(NSError* detailedError in detailedErrors) {
                NSLog(@"  DetailedError: %@", [detailedError userInfo]);
            }
        }
        else {
            NSLog(@"  %@", [error userInfo]);
        }
    }

推荐答案

您尚未这样做，建议您阅读关于

If you haven't already done so, I suggest reading the Apple documentation on Core Data : Change Management.

您需要通知第一个上下文中通过第二个上下文保存的更改。当保存上下文时，它发布 NSManagedObjectContextDidSaveNotification 。注册该通知。在处理程序方法中，合并到第一上下文中通过第二上下文保存的更改。例如：

You need to notify the first context of the changes that were saved through the second context. When saving a context, it posts a NSManagedObjectContextDidSaveNotification. Register for that notification. In the handler method, merge into the first context the changes saved through the second context. For example:

// second managed object context save

// register for the notification
[[NSNotificationCenter defaultCenter] 
    addObserver:self 
       selector:@selector(handleDidSaveNotification:)
           name:NSManagedObjectContextDidSaveNotification 
         object:secondManagedObjectContext];

// rest of the code ommitted for clarity
if (![secondManagedObjectContext save:&error]) {
    // ...
}

// unregister from notification
[[NSNotificationCenter defaultCenter] 
    removeObserver:self 
              name:NSManagedObjectContextDidSaveNotification 
            object:secondManagedObjectContext];

通知处理程序：

- (void)handleDidSaveNotification:(NSNotification *)note {
    [firstManagedObjectContext mergeChangesFromContextDidSaveNotification:note];
}

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