Block not really executing?

Question

I'm trying to use a subclass of NSThread to run some commands. Before you recommend NSOperation or GCD, YES I need to use threads.

Below is my code and my output. The block is being created and added to the array and supposedly is being dequeued and run by the thread, but I don't see any output resulting from the running of my block. Why not?

import UIKit

class ViewController: UIViewController {

    private let _queue = dispatch_queue_create("com.AaronLBratcher.ALBQueue", nil)
    private let _thread = TestThread()
    private let _lock = NSCondition()

    override func viewDidLoad() {
        super.viewDidLoad()

        _thread.start()

        var openSuccessful = false

        dispatch_sync(_queue) {[unowned self] () -> Void in
            self._lock.lock()
            self._thread.openFile("file path here", completion: { (successful) -> Void in
                print("completion block running...")
                openSuccessful = successful
                self._lock.signal()
                self._lock.unlock()
            })
            self._lock.wait()
        }

        print("open operation complete")
        print(openSuccessful)
    }


    final class TestThread:NSThread {
        var _iterations = 0
        var _lock = NSCondition()
        var _blocks = [Any]()

        func openFile(FilePath:String, completion:(successful:Bool) -> Void) {
            print("queueing openFile...")

            let block = {[unowned self] in
                self._iterations = self._iterations + 1
                print("opening file...")
                completion(successful: true)
            }

            addBlock(block)
        }

        func addBlock(block:Any) {
            _lock.lock()
            _blocks.append(block)
            _lock.signal()
            _lock.unlock()
        }

        override func main() {
            _lock.lock()
            while true {
                while _blocks.count == 0 {
                    print("waiting...")
                    _lock.wait()
                }

                print("extracting block...")
                if let block = _blocks.first {
                    _blocks.removeFirst()
                    _lock.unlock()
                    print("running block...")
                    block;
                }

                _lock.lock()
            }
        }
    }
}

Output:

queueing openFile...
waiting...
extracting block...
running block...
waiting...

Answer 1

The block isn't running because you just have block. You need block(), e.g.:

if let block = _blocks.first as? ()->() {
    _blocks.removeFirst()
    _lock.unlock()
    print("running block...")
    block()
}