iphone - openWithCompletionHandler完成处理程序参数始终= NO

我有这样的代码(我尝试从云中打开文档):

NSPredicate *pred = [NSPredicate predicateWithFormat:@"%K ENDSWITH '.card'", NSMetadataItemFSNameKey];

NSMetadataQuery *query = [[NSMetadataQuery alloc] init];
[query setSearchScopes:[NSArray arrayWithObject:NSMetadataQueryUbiquitousDocumentsScope]];
[query setPredicate:pred];

[[NSNotificationCenter defaultCenter]
 addObserver:self
 selector:@selector(queryDidFinishGathering:)
 name:NSMetadataQueryDidFinishGatheringNotification
 object:query];

[[NSNotificationCenter defaultCenter]
 addObserver:self
 selector:@selector(queryDidStartGathering:)
 name:NSMetadataQueryDidStartGatheringNotification
 object:query];

[[NSNotificationCenter defaultCenter]
 addObserver:self
 selector:@selector(queryDidUpdate:)
 name:NSMetadataQueryDidUpdateNotification
 object:query];

[query startQuery];

// ========================

- (void)queryDidFinishGathering:(NSNotification *)notification {

    NSMetadataQuery *query = [notification object];
    [query disableUpdates];
    [query stopQuery];

    [[NSNotificationCenter defaultCenter] removeObserver:self
                                                    name:NSMetadataQueryDidFinishGatheringNotification
                                                  object:query];

    for (NSMetadataItem* item in [query results]) {
        NSURL *url = [item valueForAttribute:NSMetadataItemURLKey];
        BCCardDocument *doc = [[[BCCardDocument alloc] initWithFileURL:url] autorelease];
        [doc openWithCompletionHandler:^(BOOL success) {
            if (success) {
                NSLog(@"%@", doc.card.number);
            }
        }];

    }

}

但是openWithCompletionHandler完成块的成功参数始终等于NO。可能是什么原因呢？

最佳答案

我无法确切地告诉您您需要做什么，但是我可以告诉您如何获取错误消息，以便您找出问题所在。

在BCCardDocument类的@implementation部分中，添加以下内容:

- (void)handleError:(NSError *)error userInteractionPermitted:(BOOL)userInteractionPermitted {
    NSLog(@"Error: %@ userInfo=%@", error.localizedDescription, error.userInfo);
    [super handleError:error userInteractionPermitted:userInteractionPermitted];
}