如何在swift 4中的闭包中指定类属性

我试图访问位置数据，从中获取城市名称，然后将其分配给一个变量，这样我就可以在其他地方使用它。它可以在闭包中很好地打印变量，但是当我试图通过我创建的类变量访问它时，它的值为零，代码如下，谢谢

class NewPostViewController: BaseViewController {

    @IBOutlet weak var postBodyTextField: UITextField!

    var city: String?

    @IBAction func createPostAction(_ sender: Any) {
        getCity()

        db.collection("posts").document().setData([
            "body": postBodyTextField.text,
            "location": city,
            "user": user?.displayName
        ]) { err in
            if let err = err {
                print("Error writing document: \(err)")
            } else {
                print("Document successfully written!")
            }
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
    }

    func getCity() {
        Locator.currentPosition(accuracy: .city, onSuccess: { location in
            let geocoder: CLGeocoder = CLGeocoder()
            geocoder.reverseGeocodeLocation(location, completionHandler: { location, error in
                if let location = location {
                    self.city = location[0].locality
                }
            })
        }, onFail: {_,_ in
            print("Error, couldnt get current location")
        })
    }
}

---

将

db.collection（“posts”）.document（）

geocoder.reverseGeocodeLocation(location, completionHandler: { location, error in
    if let location = location {
         self.city = location[0].locality
         db.collection("posts").document().setData( .... )
    }
})

想想/google“异步”是什么意思。您的代码没有按照编写顺序运行。尝试从
self.city
获取值后，您将分配给
self.city
。行
“location”：city
在行
self.city=location[0]之前执行。locality
。