Question

在我的应用程序中，我有Category和Sub_Category实体，它们之间有很多关系。

首先，当App第一次运行时，关系属性（category_subCategory）正在运行，如下所示：

2012-04-11 04:03:39.344 SupplyTrackerApp[27031:12f03] Saved
2012-04-11 04:03:47.423 SupplyTrackerApp[27031:fb03] Category<Category: 0x6ba4e90> (entity: Category; id: 0x6e95620 <x-coredata://00E5784E-D032-41DD-BD60-B85B0BBF8E31/Category/p1> ; data: {
    categoryID = 1;
    categoryName = Antiques;
    "category_SubCategory" =     (
        "0x6ebb4f0 <x-coredata://00E5784E-D032-41DD-BD60-B85B0BBF8E31/Sub_Category/p1>"
    );
    catetogoryDescription = "Contains a Sub categories related to Antique pieces";
})

但是当我退出应用程序并重新启动应用程序时，该关系确实存在。输出看起来像这样..

2012-04-11 04:05:04.455 SupplyTrackerApp[27038:fb03] In Cell for row at index path
2012-04-11 04:05:05.548 SupplyTrackerApp[27038:fb03] Category<Category: 0x6ecaca0> (entity: Category; id: 0x6eb4ab0 <x-coredata://00E5784E-D032-41DD-BD60-B85B0BBF8E31/Category/p1> ; data: {
    categoryID = 1;
    categoryName = Antiques;
    "category_SubCategory" = "<relationship fault: 0x6ecf0a0 'category_SubCategory'>";
    catetogoryDescription = "Contains a Sub categories related to Antique pieces";
})

这是我正在调用创建实体的地方..

-(void) loadDataIntoDocument{


    NSLog(@"In Load Data");

    dispatch_queue_t fetch=dispatch_queue_create("Data Fetcher", NULL);

    dispatch_async(fetch, ^{



            [Sub_Category createSubCategory:context];


            NSError *error;


            if (![context save:&error]) {
                NSLog(@"Whoops, couldn't save: %@", [error localizedDescription]);
            }else {


                NSLog(@"Saved");
            }


    });




    dispatch_release(fetch);


}

因此Sub_Category + Create Category文件具有以下代码。

+(Sub_Category *) createSubCategory:(NSManagedObjectContext *)context{


    Sub_Category *subCategory=nil;

    NSFetchRequest *request=[NSFetchRequest fetchRequestWithEntityName:@"Sub_Category"];

    request.predicate=[NSPredicate predicateWithFormat:@"subCategoryID=%@", @"11"];

    NSSortDescriptor *sortDescriptor=[NSSortDescriptor sortDescriptorWithKey:@"subCategoryName" ascending:YES];

    request.sortDescriptors=[NSArray arrayWithObject:sortDescriptor];



    NSError *error;

    NSArray *matches=[context executeFetchRequest:request error:&error];

    if (!matches||[matches count]>1) {
        ///errorrrrrrrrrr
    } else if([matches count]==0) {


        subCategory=[NSEntityDescription insertNewObjectForEntityForName:@"Sub_Category" inManagedObjectContext:context];

        subCategory.subCategoryID=[NSString stringWithFormat:@"%i", 11];

        subCategory.subCategoryName=@"Antiquities";

        subCategory.subCategoryDescription=@"Contains several products related to antiquities";



        subCategory.subCategory_Category =[Category createCategory:context];

    }else {
        subCategory=[matches lastObject];
    }



    return subCategory;



}

然后我调用Category + Create Category文件，其中包含以下代码。

+(Category *) createCategory:(NSManagedObjectContext *)context{


    Category *category=nil;

    NSFetchRequest *request=[NSFetchRequest fetchRequestWithEntityName:@"Category"];

    request.predicate=[NSPredicate predicateWithFormat:@"categoryID=%@", @"1"];

    NSSortDescriptor *sortDescriptor=[NSSortDescriptor sortDescriptorWithKey:@"categoryName" ascending:YES];

    request.sortDescriptors=[NSArray arrayWithObject:sortDescriptor];


    NSError *error;

    NSArray *matches=[context executeFetchRequest:request error:&error];

    if (!matches||[matches count]>1) {
        ///errorrrrrrrrrr
            } else if([matches count]==0) {

                category=[NSEntityDescription insertNewObjectForEntityForName:@"Category" inManagedObjectContext:context];

                category.categoryID=[NSString stringWithFormat:@"%d",1];

                category.categoryName=@"Antiques";

                category.catetogoryDescription=@"Contains a Sub categories related to Antique pieces";




            }else {
                category=[matches lastObject];
            }






    return category;

}

任何人都可以帮我解决这个问题。

我几天就坚持这个......

Answer 1

我看起来您正在使用dispatch_async在后台执行-save:。这可能违反了处理NSManagedObject的“线程限制”规则（简而言之，它们只应在它们创建的线程中使用。同样适用于从它们获取的任何对象）。

有关如何与Core Data进行并发的更多信息，请参阅this WWDC Session。

尝试仅使用主线程中的Core Data堆栈（以及从中获取的任何对象）。

实体之间的关系并不持久

1 个答案: