filewatch.swift

var context = FSEventStreamContext(version: 0, info: nil, retain: nil, release: nil, copyDescription: nil)
let flags   = UInt32(kFSEventStreamCreateFlagUseCFTypes | kFSEventStreamCreateFlagFileEvents)

let callback: FSEventStreamCallback = {(streamRef: ConstFSEventStreamRef, clientCallBackInfo: UnsafeMutableRawPointer?, numEvents: Int, eventPaths: UnsafeMutableRawPointer, eventFlags: UnsafePointer<FSEventStreamEventFlags>?, eventIds: UnsafePointer<FSEventStreamEventId>?) -> Void in
    DispatchQueue.main.async {
        print("HERE")
    }
}

let stream = FSEventStreamCreate(kCFAllocatorDefault, callback, &context, ([testDir] as CFArray), FSEventStreamEventId(kFSEventStreamEventIdSinceNow), 0, flags)

FSEventStreamSetDispatchQueue(stream!, DispatchQueue.global())
FSEventStreamStart(stream!)