我如何计时Cocoa应用程序？

import Foundation

class TimerExample: NSObject {
    var timer: NSTimer?

    func startTimer() {
        timer = NSTimer.scheduledTimerWithTimeInterval(1.0, target: self, selector: #selector(timerFired), userInfo: nil, repeats: true)
    }

    func stopTimer() {
        timer?.invalidate()
        timer = nil
    }

    @objc func timerFired() {
        // 在这里执行您的代码
    }
}

import Dispatch

class TimerExample {
    private var timer: DispatchSourceTimer?

    func startTimer() {
        timer = DispatchSource.makeTimerSource(flags: [], queue: DispatchQueue.main)
        timer?.schedule(deadline: .now(), repeating: 1.0)
        timer?.setEventHandler {
            // 在这里执行您的代码
        }
        timer?.resume()
    }

    func stopTimer() {
        timer?.cancel()
        timer = nil
    }
}