为什么 NSFilePresenter 协议方法永远不会被调用？

Question

我正在尝试监视本地和 iCloud 目录中的文件更改并实现了 NSFilePresenter 协议方法，但唯一被调用的方法是presentedItemAtURL.

我是否正确假设我应该能够监视本地或 iCloud 目录并在任何进程添加、修改或删除目录中的文件时收到通知。

这是 OS X 应用程序的基本代码：

- (void)awakeFromNib {
        _presentedItemURL = myDocumentsDirectoryURL;
        _presentedItemOperationQueue = [[NSOperationQueue alloc] init];
        [_presentedItemOperationQueue setMaxConcurrentOperationCount: 1];
        _fileCoordinator = [[NSFileCoordinator alloc] initWithFilePresenter:self];
}
- (NSURL*) presentedItemURL {
    FLOG(@" called %@", _presentedItemURL);
    return _presentedItemURL;
}

- (NSOperationQueue*) presentedItemOperationQueue {
    FLOG(@" called");
    return _presentedItemOperationQueue;
}

- (void)presentedItemDidChange {
    FLOG(@" called");
    dispatch_async(dispatch_get_main_queue(), ^{
        [self reloadData];
    });
}
-(void)accommodatePresentedItemDeletionWithCompletionHandler:(void (^)(NSError *errorOrNil))completionHandler
{   FLOG(@" called");
    [[NSOperationQueue mainQueue] addOperationWithBlock:^{
        [self reloadData];
    }];
    completionHandler(nil);
}
-(void)presentedSubitemDidChangeAtURL:(NSURL *)url {
    FLOG(@" called");
    dispatch_async(dispatch_get_main_queue(), ^{
        [self reloadData];
    });
}
-(void)presentedSubitemDidAppearAtURL:(NSURL *)url {
    FLOG(@" called");
    dispatch_async(dispatch_get_main_queue(), ^{
        [self reloadData];
    });

}

Answer 1

这绝不是我的最终实现，我将随着改进进行编辑/更新。但由于没有关于如何做到这一点的示例，我想我会分享一些有效的东西！没错，它有效。我可以在我的应用程序中读取该文件，同时在文本编辑中进行更改，并将更改传播到我的应用程序。希望这对芽有帮助。

PBDocument.h

@interface PBDocument : NSObject <NSFilePresenter>

@property (nonatomic, strong) NSTextView *textView;

#pragma mark - NSFilePresenter properties
@property (readonly) NSURL *presentedItemURL;
@property (readonly) NSOperationQueue *presentedItemOperationQueue;

- (instancetype)initWithContentsOfURL:(NSURL *)url error:(NSError *__autoreleasing *)outError textView:(NSTextView*)textView;

@end

PBDocument.m

@interface PBDocument ()

@property (readwrite) NSURL *presentedItemURL;
@property (readwrite) NSOperationQueue *presentedItemOperationQueue;
@property (readwrite) NSFileCoordinator *fileCoordinator;

@end

@implementation PBDocument

- (instancetype)initWithContentsOfURL:(NSURL *)url error:(NSError *__autoreleasing *)outError textView:(NSTextView*)textView {
    self = [super init];
    if (self) {
        _textView = textView;
        _presentedItemURL = url;

        _presentedItemOperationQueue = [NSOperationQueue mainQueue];

        [NSFileCoordinator addFilePresenter:self];
        _fileCoordinator = [[NSFileCoordinator alloc] initWithFilePresenter:self];

        [self readWithCoordination];
    }
    return self;
}

- (void)readWithCoordination {
    NSError *error = nil;

    [self.fileCoordinator coordinateReadingItemAtURL:_presentedItemURL options:NSFileCoordinatorReadingWithoutChanges error:&error byAccessor:^(NSURL *newURL) {
        NSLog(@"Coordinating Read");
        NSError *error = nil;
        NSFileWrapper *wrapper = [[NSFileWrapper alloc] initWithURL:newURL options:0 error:&error];

        if (!error) {
            [self readFromFileWrapper:wrapper ofType:[self.presentedItemURL pathExtension] error:&error];
        }

        if (error) @throw [NSException exceptionWithName:NSInternalInconsistencyException reason:[NSString stringWithFormat:@"%@", error] userInfo:nil];
    }];

    if (error) @throw [NSException exceptionWithName:NSInternalInconsistencyException reason:[NSString stringWithFormat:@"%@", error] userInfo:nil];
}

- (void)presentedItemDidChange {
    [self readWithCoordination];
}

@end