NSNetService.resolveWithTimeout (with success callback)

resolveWithTimeout.swift

extension NSNetService {
    func resolveWithTimeout(timeout: NSTimeInterval, success: () -> ()) {
        class NetServiceDelegate: NSObject, NSNetServiceDelegate {
            let oldDelegate: NSNetServiceDelegate?
            let netService: NSNetService
            let success: () -> ()
            var holdSelf: NetServiceDelegate?
            
            init(netService: NSNetService, success: () -> ()) {
                self.oldDelegate = netService.delegate
                self.netService = netService
                self.success = success
                super.init()
                holdSelf = self
                netService.delegate = self
            }
            
            private func finish() {
                netService.delegate = oldDelegate
                holdSelf = nil
            }
            
            private func netServiceDidResolveAddress(sender: NSNetService) {
                success()
                finish()
            }
            
            private func netService(sender: NSNetService, didNotResolve errorDict: [NSObject : AnyObject]) {
                finish()
            }
        }
        
        NetServiceDelegate(netService: self, success: success)
        self.resolveWithTimeout(timeout)
    }
}