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在过去的几个小时里，我一直在扯头发，试图弄清楚为什么这不起作用。我在 Core Data 中有一对多的关系，并且正在尝试将值正确传递给详细信息 segue。

下面是数据模型（属性是二进制数据类型）：

如果我在 configureCell: 方法中获取数据，它会给我预期的值：

- (void)configureCell:(UITableViewCell *)cell atIndexPath(NSIndexPath *)indexPath 
{ 
TBAppDelegate *delegate = (TBAppDelegate *)[[UIApplication sharedApplication] delegate];

managedObjectContext = [delegate managedObjectContext];

self.everything = [fetchedResultsController.fetchedObjects objectAtIndex:indexPath.section];

NSArray *arg = [NSKeyedUnarchiver unarchiveObjectWithData:self.everything.urls.urls];

NSLog (@"%@, [arg valueForKey:@"source"]); // this prints out a list of stored urls containing locations of jpeg images
}

我的 NSFetchedResultsController：

- (NSFetchedResultsController *)fetchedResultsController 
{ 
TBAppDelegate *delegate = (TBAppDelegate *)[[UIApplication sharedApplication] delegate];

self.managedObjectContext = delegate.managedObjectContext;

NSFetchRequest *fetchRequest = nil;

fetchRequest = [[NSFetchRequest alloc] init];

NSEntityDescription *entity = nil;

entity = [NSEntityDescription entityForName:@"Everything" inManagedObjectContext:managedObjectContext];

[fetchRequest setEntity:entity];

[fetchRequest setFetchBatchSize:INFINITY];

NSSortDescriptor *albumDescriptor = nil;

albumDescriptor = [[NSSortDescriptor alloc] initWithKey:@"album_names" ascending:NO];

NSSortDescriptor *urlDescriptor = nil;

urlDescriptor = [[NSSortDescriptor alloc] initWithKey:@"urls.urls" ascending:NO];

NSArray *sortDescriptors = nil;

sortDescriptors = [[NSArray alloc] initWithObjects:albumDescriptor, urlDescriptor, nil];

[fetchRequest setSortDescriptors:sortDescriptors];

NSFetchedResultsController *frc = nil;

frc = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:nil cacheName:@"Root"];

[frc setDelegate:self];

[self setFetchedResultsController:frc];

return frc;

}

这是我的 prepareForSegue: 方法。这部分不起作用。当我尝试设置详细视图控制器的部分计数时，它会因无法识别的选择器错误而崩溃。

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender 
{
    NSIndexPath *indexPath;

    indexPath = [self.tableView indexPathForSelectedRow];

    TBAppDelegate *delegate = (TBAppDelegate *)[[UIApplication sharedApplication] delegate];

    managedObjectContext = [delegate managedObjectContext];

    self.everything = [fetchedResultsController.fetchedObjects objectAtIndex:indexPath.section];

    NSArray *data = [NSKeyedUnarchiver unarchiveObjectWithData:self.everything.album_names];

    NSArray *urls = [NSKeyedUnarchiver unarchiveObjectWithData:self.everything.urls.urls];

    TBEverythingDetailViewController *details = segue.destinationViewController;

    details.everything = [[data objectAtIndex:indexPath.section]valueForKey:@"name"];

    self.urls.urls = [fetchedResultsController.fetchedObjects objectAtIndex:indexPath.section];

    details.everythingGroup = [urls objectAtIndex:indexPath.section];  
}

部分细节视图控制器：

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView 
{

// This is where the actual crash happens. It complains about [_NSDictionaryM urls:] unrecognized selector sent to instance
NSArray *count = [NSKeyedUnarchiver unarchiveObjectWithData:self.everythingGroup.urls.urls];

return [count count]; 
}

我觉得我在这里遗漏了一些明显的步骤，说明它为什么不起作用。我可以帮忙吗？

4

2 回答 2

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您的 self.everythinggrpup 是一个 NSDictionary，因此不会响应选择器“urls”。在某个地方，您将 NSDictionary 而不是 Everything 对象分配给 self.everythinggroup。所以你不需要这样做，或者从字典中取出所有对象，然后向它询问 url。取决于你是如何设置的。

于 2013-11-03T08:27:16.217 回答
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您确实将详细信息 EverythingGroup 设置为：

NSArray *urls = [NSKeyedUnarchiver unarchiveObjectWithData:self.everything.urls.urls];
details.everythingGroup = [urls objectAtIndex:indexPath.section];

正如我在 URLs.urls 中看到的，是一个归档到 NSData 中的字典数组。所以details.everythingGroup现在是一本字典，但你正在访问它：

NSArray *count = [NSKeyedUnarchiver unarchiveObjectWithData:self.everythingGroup.urls.urls];

它在这里崩溃是正常的。当您访问它时，它看起来details.everythingGroup应该是一个Everything.

于 2013-11-03T08:31:56.707 回答