如何在执行块后返回值？迅速 [英] how to return value after the execution of the block? Swift

问题描述

我想从函数中获取值。有功能块。当块执行时，函数已经返回值。我尝试了很多不同的方法，但他们没有帮助我。我使用 NSOperation 和Dispatch。该函数始终返回值，直到执行块为止。

I want to get a value from function. There is a block in function. When block executes the function already returns the value. I tried many different methods but they didn't help me. I used NSOperation and Dispatch. The function always returns value until execution of block.

   var superPlace: MKPlacemark!

 func returnPlaceMarkInfo(coordinate: CLLocationCoordinate2D) -> MKPlacemark? {
    let location = CLLocation(latitude: coordinate.latitude, longitude: coordinate.longitude)
    geocoder.reverseGeocodeLocation(location) { (arrayPlaceMark, error) -> Void in
            if error == nil {
                let firstPlace = arrayPlaceMark!.first!
                let addressDictionaryPass = firstPlace.addressDictionary as! [String : AnyObject]

                self.superPlace = MKPlacemark(coordinate: location.coordinate, addressDictionary: addressDictionaryPass)
            }
        }

    return superPlace
}

推荐答案

你不能简单地回到这里作为reverseGeocodeLocation函数异步运行，因此您需要使用自己的完成块：

You cannot simply return here as the reverseGeocodeLocation function is running asynchronously so you will need to use your own completion block:

var superPlace: MKPlacemark!

func getPlaceMarkInfo(coordinate: CLLocationCoordinate2D, completion: (superPlace: MKPlacemark?) -> ()) {
    let location = CLLocation(latitude: coordinate.latitude, longitude: coordinate.longitude)
    geocoder.reverseGeocodeLocation(location) { (arrayPlaceMark, error) -> Void in
        if error == nil {
            let firstPlace = arrayPlaceMark!.first!
            let addressDictionaryPass = firstPlace.addressDictionary as! [String : AnyObject]

            self.superPlace = MKPlacemark(coordinate: location.coordinate, addressDictionary: addressDictionaryPass)
            completion(superPlace: superPlace)
        } else {
            completion(superPlace: nil)
        }
    } 
}

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