如何在执行块后返回值？迅速
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
}
答
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)
}
}
}