NSPrivateQueueConcurrencyType Not saving properly

问题

The following method gets called in order to populate my Core-Data after AFNetworking fetches information from my app server.

The information seems to be perfectly working as when the table is updated I can see the new information being updated in the UITableView.

Now the problem that I have is that even tho I can see the information ( after it has been fetches from the server, stored into Core-data and refetches to display in my UITableView) If I then go and close my app and re open it, the information is not there anymore.

It seems as if the information is not persistent and the problem seems to be the thread. given that if I remove the thread option in my method everything works fine.

What am I missing?? I have tried most things that I came across but I can't seem to find a solution.

NSManagedObjectContext *childContext = [[NSManagedObjectContext alloc]
                                        initWithConcurrencyType:NSPrivateQueueConcurrencyType];
childContext.parentContext = managedObjectContext;
myModel.context = childContext;


   [childContext performBlock:^{
// ... Lots Controller logic code that then calls the class myModel where all my Core-Data save methods are

    // Sort Wall Pictures
                    if ( [dataHolder[@"verb"] isEqualToString:@"addWallPicture"] ) {
                        data = @{  @"resourceID":dataHolder[@"_id"][@"$id"],
                                   @"resourceName":dataHolder[@"details"][@"resourceName"],
                                   @"author":@{ @"id":dataHolder[@"userId"][@"$id"],
                                                @"username":dataHolder[@"details"][@"authorName"] },
                                   @"likesNumber":@0,
                                   @"likesPeople":@[]
                                   };

                        [myModel saveSocialWall:data date:date verb:dataHolder[@"verb"] code:dataHolder[@"_id"][@"$id"] myUser:myUser];
                        continue;
                    }
[childContext save:&error];
}];

回答1:

You have to save the main context as well at some point, e.g. after saving the child context.

Saving the child context saves only to the main context, and saving the main context saves to the store file.

Like this (written on the phone, there will be syntax errors):

// ...
[childContext save:&error];
[mainContext performBlock:^{
    [mainContext save:&error];
}];

In Swift 2.0 that would be:

do {
    try childContext.save()
    mainContext.performBlock { 
        do {
            try mainContext.save()
        } catch let err as NSError {
            print("Could not save main context: \(err.localizedDescription)")
        }
    }
} catch let err as NSError {
    print("Could not save private context: \(err.localizedDescription)")
}

来源：https://stackoverflow.com/questions/19328394/nsprivatequeueconcurrencytype-not-saving-properly

标签

objective-c

cocoa-touch

cocoa

core-data

nsmanagedobject