ios - iPad 应用程序中核心数据的错误

Question

我正在开发一个将利用核心数据的应用程序。我包含了 CoreData.Framework，但应用程序抛出以下错误:

  "_OBJC_CLASS_$_NSFetchedResultsController", referenced from:
      objc-class-ref-to-NSFetchedResultsController in RootViewController.o
  "_OBJC_CLASS_$_NSEntityDescription", referenced from:
      objc-class-ref-to-NSEntityDescription in RootViewController.o
  "_OBJC_CLASS_$_NSFetchRequest", referenced from:
      objc-class-ref-to-NSFetchRequest in RootViewController.o
ld: symbol(s) not found

如果我禁用以下应用程序编译时没有错误:

#pragma mark -
#pragma mark Fetched results controller

/*- (NSFetchedResultsController *)fetchedResultsController {

    if (fetchedResultsController != nil) {
        return fetchedResultsController;
    }*/

    /*
     Set up the fetched results controller.
     */
    // Create the fetch request for the entity.
  /*  NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    // Edit the entity name as appropriate.
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Event" inManagedObjectContext:managedObjectContext];
    [fetchRequest setEntity:entity];

    // Set the batch size to a suitable number.
    [fetchRequest setFetchBatchSize:20];

    // Edit the sort key as appropriate.
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"timeStamp" ascending:NO];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];

    [fetchRequest setSortDescriptors:sortDescriptors];

    // Edit the section name key path and cache name if appropriate.
    // nil for section name key path means "no sections".
    NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"];
    aFetchedResultsController.delegate = self;
    self.fetchedResultsController = aFetchedResultsController;

    [aFetchedResultsController release];
    [fetchRequest release];
    [sortDescriptor release];
    [sortDescriptors release];

    return fetchedResultsController;
}    */


#pragma mark -
#pragma mark Fetched results controller delegate

/*- (void)controllerWillChangeContent:(NSFetchedResultsController *)controller {
    [self.tableView beginUpdates];
}


- (void)controller:(NSFetchedResultsController *)controller didChangeSection:(id <NSFetchedResultsSectionInfo>)sectionInfo
           atIndex:(NSUInteger)sectionIndex forChangeType:(NSFetchedResultsChangeType)type {

    switch(type) {
        case NSFetchedResultsChangeInsert:
            [self.tableView insertSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [self.tableView deleteSections:[NSIndexSet indexSetWithIndex:sectionIndex] withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}


- (void)controller:(NSFetchedResultsController *)controller didChangeObject:(id)anObject
       atIndexPath:(NSIndexPath *)indexPath forChangeType:(NSFetchedResultsChangeType)type
      newIndexPath:(NSIndexPath *)newIndexPath {

    UITableView *tableView = self.tableView;

    switch(type) {

        case NSFetchedResultsChangeInsert:
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeDelete:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            break;

        case NSFetchedResultsChangeUpdate:
            [self configureCell:[tableView cellForRowAtIndexPath:indexPath] atIndexPath:indexPath];
            break;

        case NSFetchedResultsChangeMove:
            [tableView deleteRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationFade];
            [tableView insertRowsAtIndexPaths:[NSArray arrayWithObject:newIndexPath]withRowAnimation:UITableViewRowAnimationFade];
            break;
    }
}


- (void)controllerDidChangeContent:(NSFetchedResultsController *)controller {
    [self.tableView endUpdates];
}

有什么想法我可能需要添加或遗漏了什么吗？

这里编辑的是头文件:

#import <UIKit/UIKit.h>
#import <CoreData/CoreData.h>


@class DetailViewController;

@interface RootViewController : UITableViewController <NSFetchedResultsControllerDelegate> {

    DetailViewController *detailViewController;

    NSFetchedResultsController *fetchedResultsController;
    NSManagedObjectContext *managedObjectContext;
}

@property (nonatomic, retain) IBOutlet DetailViewController *detailViewController;

@property (nonatomic, retain) NSFetchedResultsController *fetchedResultsController;
@property (nonatomic, retain) NSManagedObjectContext *managedObjectContext;

- (void)insertNewObject:(id)sender;

@end

为了使事情复杂化，我使用本教程获得了这些结果:

http://www.iphonedevsdk.com/forum/iphone-sdk-development/62217-simplest-way-make-split-controller-tab-bar-controller.html

Answer 1

我遇到了完全相同的问题。对于那些遇到类似问题并发表这篇文章的其他人，McCannon 的评论帮助了我；我忘记将核心数据框架添加到我项目的构建阶段。如果您不知道如何操作，请按照此处的说明进行操作:How to "add existing frameworks" in Xcode 4?