Swift闭包，调用中参数＃1的参数丢失

Question

Hello all who want to help. I am trying to do a callback function when I get my location updated. But I run into a problem that I have no idea how to solve.

class ViewController: UIViewController {

@IBOutlet weak var currentTemperatureLabel: UILabel?
@IBOutlet weak var currentHumidityLabel: UILabel?
@IBOutlet weak var currentPrecipitationLabel: UILabel?
@IBOutlet weak var currentWeatherIcon: UIImageView?
@IBOutlet weak var currentWeatherSummary: UILabel?

private let APIKey = "someString"

let location = LocationService(){
    callBackFunction in
    loadData()
}

func loadData()
{
    let forecastService = ForecastService(APIKey: APIKey)
    forecastService.getForecast(location.latitude, long: location.longitude)
        {
            (let currentW) in
            if let currentWeather = currentW
            {
                dispatch_async(dispatch_get_main_queue())
                    {

                        if tjekIfNil(currentWeather.temperature)
                        {
                            self.currentTemperatureLabel?.text = "\(currentWeather.temperature!)°"
                        }
                        if tjekIfNil(currentWeather.humidity)
                        {
                            self.currentHumidityLabel?.text = "\(currentWeather.humidity!)%"
                        }
                        if tjekIfNil(currentWeather.precipProbability)
                        {
                            self.currentPrecipitationLabel?.text = "\(currentWeather.precipProbability!)%"
                        }
                        if tjekIfNil(currentWeather.icon)
                        {
                            self.currentWeatherIcon?.image = currentWeather.icon
                        }
                        if tjekIfNil(currentWeather.summary)
                        {
                            self.currentWeatherSummary?.text = currentWeather.summary
                        }
                }
            }
    }
}

override func viewDidLoad() {
    super.viewDidLoad()
        location.requestPermission()
        location.getLocation()
    }

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

}

The error occurs here when I call loadData()

let location = LocationService(){
    callBackFunction in
    println("data is loading")
    loadData()
}

Here is the LocationService class

import CoreLocation
class LocationService: NSObject, CLLocationManagerDelegate
{
var locationManager : CLLocationManager!
var location : CLLocation?
var longitude : Double?
var latitude : Double?
let callBackFunction : ()->()

init(callBackFunc: (Void->Void))
{
    locationManager = CLLocationManager()
    callBackFunction = callBackFunc
}

func requestPermission()
{
    locationManager.requestWhenInUseAuthorization()
}
func getLocation()
{
    if(CLLocationManager.authorizationStatus() == CLAuthorizationStatus.AuthorizedWhenInUse)
    {
        locationManager.delegate = self
        locationManager.desiredAccuracy = kCLLocationAccuracyBest
        locationManager.startUpdatingLocation()

    }else
    {
        location = nil
        longitude = nil
        latitude = nil
    }

}
func locationManager(manager: CLLocationManager!, didUpdateLocations locations: [AnyObject]!)
{
    location = locationManager.location
    if tjekIfNil(location?.coordinate.longitude)
    {longitude = location!.coordinate.longitude}
    if tjekIfNil(location?.coordinate.latitude)
    {latitude = location!.coordinate.latitude}
    locationManager.stopUpdatingLocation()
    println(longitude)
    println(latitude)
    callBackFunction()
}

}

From what I have found myself it is something about calling loadData() as a class function while it is a instance function. Im still very new to swift so I don't really know how to solve the problem, so any help would be greatly appreciated.

Edit: I found the solotion. The reason that the error was popping op was because the function loadData() was initilaized but the callBackFunction wasn't properly initilaized. I solved it by moving the callBackFunction to getLocation() instead of the initialization.

Answer 1

The issue is with the way you are passing the callback, instead of:

let location = LocationService(){
    callBackFunction in
    loadData()
}

You need to pass the callback like:

let location = LocationService(callBackFunc:loadData)