Hi all,
I’ve never used NSFileCoordinator class, simply because I haven’t had any need
for it until now. And now that I’m about to need it rather soon, I’m trying to
get a grasp on it, but it does’t go very well so far. Even though the
documentation reads pretty clear, I don’t seem to get it correctly. Also, I
haven’t found any example online, which would be of any value to me, so I’m
taking my chances here. In order to begin to understand it, I’ll start with the
simplest real case scenario, for which I don’t even understand yet whether
NSFileCoordinator is the way to go.
Let’s say, I have a bunch of directories in a parent directory (so, all are at
the same level in the file system hierarchy), which I want to compress and pack
in a ZIP archive (for example) programatically (e.g. using libarchive). After
selecting which directories to zip, I’d like to ensure that once the zipping
operation has started, any changes to all files and directories in the
hierarchies of selected directories to be packed will stay unchanged, until the
zipping operation is complete. That means, no file anywhere in the hierarchies
should be modified in any way and no directory or file anywhere in the
hierarchies should be added, deleted or moved.
I thought I would achieve this by using one NSFileCoordinator and a bunch
NSFileAccessIntent objects, each for every directory at the top level of the
hierarchies. The intents will be for reading without changing, because that’s
what I want to do; just to read those directories and files (and zip them)
without making any changes to them. The code would be something like this (I
want to do the operation asynchronously):
NSMutableArray *intents = [NSMutableArray arrayWithCapacity:[sources count]];
for (NSURL *source in sources)
[intents addObject:[NSFileAccessIntent readingIntentWithURL:source
options:NSFileCoordinatorReadingWithoutChanges]];
NSFileCoordinator *coordinator = [[NSFileCoordinator alloc]
initWithFilePresenter:nil];
[coordinator coordinateAccessWithIntents:intents queue:[NSOperationQueue new]
byAccessor:^(NSError *error)
{
// Do the zipping here.
}];
It looks simple and straightforward, but it doesn’t really work as I thought it
would. Once the operation is started, I can modify files and directories the
way I described above, from within the same application/process, as well as
others (using NSFileCoordinator approach), like Finder.
Hence, I’d really appreciate if someone can point me in the right direction.
For example, what needs to be done to achieve this simple example I described
above. Once I get some pointers, I may start understanding those classes and
documentation in the right way and work myself through more complex examples
and use cases.
Thanks,
-- Dragan
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