NSMetadataQueryDidFinishGatheringNotification从来没有所谓

问题描述：

试图运行下面的代码：NSMetadataQueryDidFinishGatheringNotification从来没有所谓

#import <Foundation/Foundation.h> 

@interface FileQuery : NSObject 

@end 

@interface FileQuery() 

@property (nonatomic, strong) NSMetadataQuery *query; 
@property (nonatomic, strong) NSMutableArray<NSURL *> *fileArray; 

@end 

@implementation FileQuery 

-(void)stopQuery { 
    if (_query) { 

    NSLog(@"No longer watching iCloud dir..."); 

    [[NSNotificationCenter defaultCenter] removeObserver:self name:NSMetadataQueryDidFinishGatheringNotification object:nil]; 
    [[NSNotificationCenter defaultCenter] removeObserver:self name:NSMetadataQueryDidUpdateNotification object:nil]; 
    [_query stopQuery]; 
    _query = nil; 
    _fileArray = nil; 
    } 
} 

-(BOOL)startQuery:(NSString *)suffix { 
    [_query stopQuery]; 

    dispatch_async(dispatch_get_global_queue(0, 0), ^{ 
    [[NSNotificationCenter defaultCenter] addObserver:self 
              selector:@selector(processFiles:) 
               name:NSMetadataQueryDidFinishGatheringNotification 
               object:nil]; 
    [[NSNotificationCenter defaultCenter] addObserver:self 
              selector:@selector(processFiles:) 
               name:NSMetadataQueryDidUpdateNotification 
               object:nil]; 

    _query = [NSMetadataQuery new]; 
    if (_query) { 
     NSLog(@"aa"); 
     _fileArray = [NSMutableArray new]; 
     [_query setSearchScopes:@[NSMetadataQueryLocalComputerScope]]; 
     [_query setPredicate:[NSPredicate predicateWithFormat:@"%K BEGINSWITH %@", 
          NSMetadataItemFSNameKey, suffix]]; 
     dispatch_async(dispatch_get_main_queue(), ^{ 
     if ([_query startQuery]) { 
      [_query enableUpdates]; 
      NSLog(@"Finished with query = %@, predicate = %@", _query, _query.predicate); 
     } 
     }); 
    } 
    }); 

    NSLog(@"bb"); 
    return TRUE; 
} 

- (void)processFiles:(NSNotification *)notification { 
    [_query disableUpdates]; 

    // The query reports all files found, every time. 
    NSArray * queryResults = [_query results]; 
    NSLog(@"Results = %@", queryResults); 
    for (NSMetadataItem * result in queryResults) { 
    NSURL * fileURL = [result valueForAttribute:NSMetadataItemURLKey]; 

    NSLog(@"file = %@", fileURL); 
    [_fileArray addObject:fileURL]; 
    } 

    [self stopQuery]; 
} 

@end 

int main(int argc, char *argv[]) { 
    if (argc != 2) { 
    NSLog(@"Error in number of params"); 
    return 0; 
    } 

    NSString *s = [NSString stringWithFormat:@"%s", argv[1]]; 
    NSLog(@"suffix = %@", s); 

    FileQuery *q = [FileQuery new]; 

    if ([q startQuery:s]) { 
    while(true) { 
     NSLog(@"1"); 
     sleep(100); 
    } 
    } else { 
    NSLog(@"query failed"); 
    } 

    return 0; 
}

出于某种原因，NSMetadataQueryDidFinishGatheringNotification永远不会被调用。

此外，NSMetadataQueryDidUpdateNotification通知也永远不会被调用。

任何人有任何想法，为什么？有没有人有更好的想法Spotlight搜索文件？

非常感谢！

答

当我做一个修改时，你的代码在我的机器上工作。相反，在循环中调用sleep的，叫CFRunLoopRun()：

int main(int argc, char *argv[]) { 
    ... 

    if ([q startQuery:s]) { 
     CFRunLoopRun(); 
    } else { 
     NSLog(@"query failed"); 
    } 

    return 0; 
}

的通知机制是使用运行循环实现的，所以你必须有一个正在运行的为它做它的魔力。

NSMetadataQueryDidFinishGatheringNotification从来没有所谓

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