核心数据和线程/大中央调度 [英] Core Data and threads / Grand Central Dispatch

问题描述

我是Grand Central Dispatch（GCD）和Core Data的初学者，我需要您帮助使用Core Data与CGD，这样当我添加40.000条记录到Core Data时，UI不会被锁定。

I'm a beginner with Grand Central Dispatch (GCD) and Core Data, and I need your help to use Core Data with CGD, so that the UI is not locked while I add 40.000 records to Core Data.

我知道CD不是线程安全的，所以我必须使用另一个上下文，然后保存数据和合并上下文，就我能从一些文章中理解。

I know that CD is not thread safe, so I have to use another context, and then save the data and merge contexts, as far as I was able to understand from some articles.

我现在还做不到的是把它们放在一起。

What I couldn't do yet, is put the pieces together.

我需要您的帮助。

我有：

/*some other code*/

for (NSDictionary *memberData in arrayWithResult) {

    //get the Activities for this member
    NSArray *arrayWithMemberActivities = [activitiesDict objectForKey:[memberData objectForKey:@"MemberID"]];

    //create the Member, with the NSSet of Activities
    [Members createMemberWithDataFromServer:memberData
                         andActivitiesArray:arrayWithMemberActivities
                              andStaffArray:nil
                           andContactsArray:nil
                     inManagedObjectContext:self.managedObjectContext];
}

如何将其转换为在后台工作，

How can I transform this to work on the background, and then, when done saving, save the data and update the UI, without blocking the UI while saving the 40.000 objects?

推荐答案

这里有一个很好的例子，你试试。如果您有任何问题，欢迎随时回来：

Here's a good example for you to try. Feel free to come back if you have any questions:

self.mainThreadContext... // This is a reference to your main thread context
NSPersistentStoreCoordinator *mainThreadContextStoreCoordinator = [self.mainThreadContext persistentStoreCoordinator];
dispatch_queue_t request_queue = dispatch_queue_create("com.yourapp.DescriptionOfMethod", NULL);
dispatch_async(request_queue, ^{

    // Create a new managed object context
    // Set its persistent store coordinator
    NSManagedObjectContext *newMoc = [[NSManagedObjectContext alloc] init];
    [newMoc setPersistentStoreCoordinator:mainThreadContextStoreCoordinator]];

    // Register for context save changes notification
    NSNotificationCenter *notify = [NSNotificationCenter defaultCenter];
    [notify addObserver:self 
               selector:@selector(mergeChanges:) 
                   name:NSManagedObjectContextDidSaveNotification 
                 object:newMoc];

    // Do the work
    // Your method here
    // Call save on context (this will send a save notification and call the method below)
    BOOL success = [newMoc save:&error];
    if (!success)
        // Deal with error
    [newMoc release];
});
dispatch_release(request_queue);

并响应上下文保存通知：

And in response to the context save notification:

- (void)mergeChanges:(NSNotification*)notification 
{
    dispatch_async(dispatch_get_main_queue(), ^{
        [self.mainThreadContext mergeChangesFromContextDidSaveNotification:notification waitUntilDone:YES];
    });
}

并且不要忘记从观察员完成后台线程上下文。

And don't forget to remove the observer from the notification center once you are done with the background thread context.

[[NSNotificationCenter defaultCenter] removeObserver:self];

这篇关于核心数据和线程/大中央调度的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！