How to monitor a folder for new files in swift?

Question

How would I monitor a folder for new files in swift, without polling (which is very inefficient)? I\'ve heard of APIs such as kqueue and FSEvents - but I\'m not sure it\'s p

Answer 1

I've tried to go with these few lines. So far seems to work.

class DirectoryObserver {

    deinit {

        dispatch_source_cancel(source)
        close(fileDescriptor)
    }

    init(URL: NSURL, block: dispatch_block_t) {

        fileDescriptor = open(URL.path!, O_EVTONLY)
        source = dispatch_source_create(DISPATCH_SOURCE_TYPE_VNODE, UInt(fileDescriptor), DISPATCH_VNODE_WRITE, dispatch_queue_create(nil, DISPATCH_QUEUE_CONCURRENT))
        dispatch_source_set_event_handler(source, { dispatch_async(dispatch_get_main_queue(), block) })
        dispatch_resume(source)
    }

    //

    private let fileDescriptor: CInt
    private let source: dispatch_source_t
}

Be sure to not get into retain cycle. If you are going to use owner of this instance in block, do it safely. For example:

self.directoryObserver = DirectoryObserver(URL: URL, block: { [weak self] in

    self?.doSomething()
})