如何在执行功能之前等待Swift中的变量? (迅速) [英] How to wait for variable in Swift before executing function? (Swift)
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问题描述
下面是我的代码.我想要Poststring中的纬度和经度"值.但是当他执行后字符串操作时，我的值仍然为零，因为swift尚未更新位置.那么，如何在后字符串获得值之前等待纬度和经度?我听到了一些didset的信息，但是我不知道如何使用它以及在哪里使用它.
below is my code. I want the value for Latitude and Longitude in my Poststring. But When he do the poststring my values are still nil because swift didn't update the location yet. So how can I wait for latitude and longitude before poststring gets the Values? I heard something of didset but I don't know how to use it and where I have to use it.
import Foundation
import CoreLocation
protocol FeedmodelProtocol: class {
func itemsDownloaded(items: NSArray)
}
class Feedmodel: NSObject, URLSessionDataDelegate, CLLocationManagerDelegate {
weak var delegate: FeedmodelProtocol!
let locationManager = CLLocationManager() // create Location Manager object
var latitude : Double?
var longitude : Double?
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
guard let location: CLLocationCoordinate2D = manager.location?.coordinate else { return }
// set the value of lat and long
latitude = location.latitude
longitude = location.longitude
}
func downloadItems() {
self.locationManager.requestAlwaysAuthorization()
// For use in foreground
// You will need to update your .plist file to request the authorization
self.locationManager.requestWhenInUseAuthorization()
if CLLocationManager.locationServicesEnabled() {
locationManager.delegate = self
locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters
locationManager.startUpdatingLocation()
}
let myUrl = URL(string: "http://example.com/stock_service4.php");
let defaultSession = Foundation.URLSession(configuration: URLSessionConfiguration.default)
var request = URLRequest(url:myUrl!)
request.setValue("application/x-www-form-urlencoded", forHTTPHeaderField: "Content-Type")
request.httpMethod = "POST"
var postString = ""
if let lat = latitude, let long = longitude {
locationManager.stopUpdatingLocation()
postString = "lati=\(Int(lat))&longi=\(Int(long))"
// do task here now that postString is not empty
}
request.httpBody = postString.data(using: .utf8)
let task = defaultSession.dataTask(with: request) { data, response, error in
guard let data = data, error == nil else { // check for fundamental networking error
print("error=\(String(describing: error))")
return
}
if let httpStatus = response as? HTTPURLResponse, httpStatus.statusCode != 200 { // check for http errors
print("statusCode should be 200, but is \(httpStatus.statusCode)")
print("response = \(String(describing: response))")
print("error=\(String(describing: error))")
}
let responseString = String(data: data, encoding: .utf8)
print("responseString = \(String(describing: responseString))")
print("error=\(String(describing: error))")
self.parseJSON(data)
}
task.resume()
}
func parseJSON(_ data:Data) {
var jsonResult = NSArray()
do{
jsonResult = try JSONSerialization.jsonObject(with: data, options:JSONSerialization.ReadingOptions.allowFragments) as! NSArray;
} catch let error as NSError {
print(error)
}
var jsonElement = NSDictionary()
let stocks = NSMutableArray()
for i in 0 ..< jsonResult.count
{
print(jsonResult)
jsonElement = jsonResult[i] as! NSDictionary
let stock = Stockmodel()
//the following insures none of the JsonElement values are nil through optional binding
if let Datum = jsonElement["Datum"] as? String,
let Tankstelle = jsonElement["Tankstelle"] as? String,
let Kraftstoff1 = jsonElement["Kraftstoff1"] as? String,
let Preis1 = jsonElement["Preis1"] as? String,
let Kraftstoff2 = jsonElement["Kraftstoff2"] as? String,
let Preis2 = jsonElement["Preis2"] as? String,
let Notiz = jsonElement["Notiz"] as? String,
let longitude = jsonElement["longitude"] as? String,
let latitude = jsonElement["latitude"] as? String
{
print (Datum)
print(Tankstelle)
print(Kraftstoff1)
print(Preis1)
print(Kraftstoff2)
print(Preis2)
print(Notiz)
print(longitude)
print(latitude)
stock.Datum = Datum
stock.Tankstelle = Tankstelle
stock.Kraftstoff1 = Kraftstoff1
stock.Preis1 = Preis1
stock.Kraftstoff2 = Kraftstoff2
stock.Preis2 = Preis2
stock.Notiz = Notiz
stock.longitude = longitude
stock.latitude = latitude
}
stocks.add(stock)
}
DispatchQueue.main.async(execute: { () -> Void in
self.delegate.itemsDownloaded(items: stocks)
})
}
}
谢谢！
推荐答案
每次更新位置时都会调用函数locationManager(_:didUpdateLocations:).因此，您应该像这样在位置管理器中添加downloadItems():
The function locationManager(_:didUpdateLocations:) is called every time when the location is update. So you should add downloadItems() in the location manager like this :
func locationManager(_ manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
guard let location: CLLocationCoordinate2D = manager.location?.coordinate else { return }
// set the value of lat and long
latitude = location.latitude
longitude = location.longitude
downloadItems()
}
请参阅有关 locationManager(_:didUpdateLocations :) 的文档
这篇关于如何在执行功能之前等待Swift中的变量? (迅速)的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
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