Question

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openWithCompletionHandler完成块的成功参数总是等于NO。可能是什么原因？

Answer 1

我无法确切地告诉你你需要做什么，但我可以告诉你如何得到错误信息，以便你能够弄明白。

在BCCardDocument班级@implementation部分，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];
}

Answer 2

我有非常相似的代码，它工作正常。我假设您的BCCardDocument是UIDocument的子类？如果是这样，它需要有这两种方法：

- (id)contentsForType:(NSString *)typeName error:(NSError **)outError

- (BOOL)loadFromContents:(id)contents
              ofType:(NSString *)typeName
               error:(NSError *__autoreleasing *)outError {

唯一的另一个区别是我没有调用stopQuery。

openWithCompletionHandler完成处理程序参数always = NO

2 个答案: