Question

我一直在四处寻找，并且在功能完成之前没有找到防止任何事情发生的方法。基本上，函数之下的事件发生在函数之前。让我告诉你代码和控制台输出。

代码：

if locationSwitch.isOn == true {
            let url = "https://maps.googleapis.com/maps/api/geocode/json?latlng=\(location.latitude),\(location.longitude)&result_type=locality&key=AIzaSyDI-ZacHyPbLchRhkoaUTDokwj--z_a_jk"
            loadUrl(url: url) { optionalLocation in
                guard let nonOptionalLocation = optionalLocation else {
                    // Location was nil; Handle error case here
                    return
                }
                // Do something with your location here, like setting UI or something
                print("Optional Location: \(optionalLocation)")
                print("nonOptional Location: \(nonOptionalLocation)")
                cityState = nonOptionalLocation
                print("cityState: \(cityState)")
                print("Within Func")
            }
            print("Within If")
        } else {
            lat = 0.0
            lng = 0.0
            cityState = ""
        }
        print("After If")
        print("cityState Outside If Statement: \(cityState)")
        CoreDataHandler.savePhotoObject(locationCoordinateLatitude: lat, locationCoordinateLongitude: lng, locationLocality: cityState, dateCreated: date, discription: discriptionBox.text!, photo: selectedImageData!)
    }

控制台输出：

Before If
Within If
After If
cityState Outside If Statement:
Optional Location: Optional("San Francisco, CA, USA")
nonOptional Location: San Francisco, CA, USA
cityState: San Francisco, CA, USA
Within Func

如你所见

Optional Location: Optional("San Francisco, CA, USA")
nonOptional Location: San Francisco, CA, USA
cityState: San Francisco, CA, USA
Within Func

应该在

之前

Within If

我相信这种情况正在发生，因为loadUrl函数需要很长时间才能完成代码覆盖它并完成其下的代码然后loadUrl完成，然后在其他所有内容后打印。除了在nonOptionalLocation函数完成后调用设置为等于loadUrl的变量并且因为loadUrl在其余代码之后结束时，这不会成为问题应该等于nonOptionalLocation的变量实际上等于""。

有人知道现在如何完成这项工作我认为我需要阻止任何事情发生，直到loadUrl完成，但如果您知道另一种方法，请分享。谢谢。

Answer 1

loadUrl异步工作，只需将数据返回完成块后执行代码

if locationSwitch.isOn == true {
    loadUrl(url: url) { optionalLocation in
        guard let nonOptionalLocation = optionalLocation else {
            // Location was nil; Handle error case here
            return
        }
        // Do something with your location here, like setting UI or something
        print("Optional Location: \(optionalLocation)")
        print("nonOptional Location: \(nonOptionalLocation)")
        cityState = nonOptionalLocation
        print("cityState: \(cityState)")
        print("Within Func")
        DispatchQueue.main.async {
            CoreDataHandler.savePhotoObject(locationCoordinateLatitude: lat, locationCoordinateLongitude: lng, locationLocality: cityState, dateCreated: date, discription: discriptionBox.text!, photo: selectedImageData!)
        }
    }
} else {
    CoreDataHandler.savePhotoObject(locationCoordinateLatitude: 0.0, locationCoordinateLongitude: 0.0, locationLocality: "", dateCreated: date, discription: discriptionBox.text!, photo: selectedImageData!)
}

Answer 2

您是否使用过DispatchQueue.main.sync {}，它可能会暂时停留在您的用户界面中一段时间不好但如果您对此没有任何问题，那么您可以试试这个。

if locationSwitch.isOn{

        DispatchQueue.main.sync {

            let url = "https://maps.googleapis.com/maps/api/geocode/json?latlng=\(location.latitude),(location.longitude)&result_type=locality&key=AIzaSyDI-ZacHyPbLchRhkoaUTDokwj--z_a_jk"

            loadUrl(url: url) { optionalLocation in
                guard let nonOptionalLocation = optionalLocation else {
                    return
                }

                print("Optional Location: \(optionalLocation)")
                print("nonOptional Location: \(nonOptionalLocation)")
                cityState = nonOptionalLocation
                print("cityState: \(cityState)")
                print("Within Func")
            }
        }
        print("Within If")
    } else {
        lat = 0.0
        lng = 0.0
        cityState = ""
    }
    print("After If")
    print("cityState Outside If Statement: \(cityState)")
    CoreDataHandler.savePhotoObject(locationCoordinateLatitude: lat, locationCoordinateLongitude: lng, locationLocality: cityState, dateCreated: date, discription: discriptionBox.text!, photo: selectedImageData!)

如何阻止任何事情发生直到func完成？

2 个答案: