iOS Swift - CLGeocoder completionHandler block

Question

我正在尝试将位置 (CLLocation) 解析为字符串。

    func locationToString (currentLocation: CLLocation) -> String? {
    var whatToReturn: String?
    CLGeocoder().reverseGeocodeLocation(currentLocation, completionHandler: { (placemarks: [AnyObject]!, error: NSError!) in
        if error == nil && placemarks.count > 0 {
            let location = placemarks[0] as CLPlacemark
            whatToReturn = "\(location.locality) \(location.thoroughfare) \(location.subThoroughfare)"

        }
    })
    return whatToReturn
}

显然，whatToReturn 总是返回 null，因为 completionHandler 在后台运行。 我很难理解如何在 completionHandler 完成时更新我的​​字符串？

谢谢。

Answer 1

如果您想在 textField 中使用您的字符串，如评论中所示，请执行以下操作:

func getAndDisplayLocationStringForLocation(currentLocation: CLLocation) {
    CLGeocoder().reverseGeocodeLocation(currentLocation, completionHandler: { (placemarks: [AnyObject]!, error: NSError!) in
        if error == nil && placemarks.count > 0 {
            let location = placemarks[0] as CLPlacemark
            self.textField.text = "\(location.locality) \(location.thoroughfare) \(location.subThoroughfare)"

        }
    })
}

但是，如果您需要在其他地方访问，也许可以将闭包作为 arg 传递:

func getAndDisplayLocationStringForLocation(currentLocation: CLLocation, withCompletion completion: (string: String?, error?, error: NSError?) -> ()) {
    CLGeocoder().reverseGeocodeLocation(currentLocation, completionHandler: { (placemarks: [AnyObject]!, error: NSError!) in
        if error == nil && placemarks.count > 0 {
            let location = placemarks[0] as CLPlacemark
            completion(string: "\(location.locality) \(location.thoroughfare) \(location.subThoroughfare)", error: nil)

        } else {
            completion(nil, error)
        }
    })
}

然后像这样调用:

yourModel.getAndDisplayLocationStringForLocation(someLocation) { (string: String?, error: NSError?) -> () in
    if (error == nil) {
        self.textField.text = string
    }
}

您可能希望以不同方式处理错误等。这应该足以让您入门。