如果位置关闭，swift 2会阻止程序运行

import CoreLocation

class ViewController: UIViewController, CLLocationManagerDelegate {
    let locationManager = CLLocationManager()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 检查位置服务是否可用
        if CLLocationManager.locationServicesEnabled() {
            locationManager.delegate = self
            locationManager.requestWhenInUseAuthorization()
            locationManager.startUpdatingLocation()
        } else {
            // 位置服务被关闭的处理逻辑
            showAlert(message: "位置服务已关闭")
        }
    }
    
    // CLLocationManagerDelegate方法，处理位置更新
    func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
        // 处理位置更新的逻辑
    }
    
    // CLLocationManagerDelegate方法，处理位置服务状态改变
    func locationManager(_ manager: CLLocationManager, didChangeAuthorization status: CLAuthorizationStatus) {
        if status == .denied {
            // 位置服务被拒绝的处理逻辑
            showAlert(message: "位置服务被拒绝")
        }
    }
    
    // 显示警告消息的方法
    func showAlert(message: String) {
        let alert = UIAlertController(title: "警告", message: message, preferredStyle: .alert)
        let okAction = UIAlertAction(title: "确定", style: .default, handler: nil)
        alert.addAction(okAction)
        present(alert, animated: true, completion: nil)
    }
}