A method without parameters is calling for an argu

I have a class named Location that has several methods in it that do not have any parameters.

However, when I try to create a variable with the result of the method, it wants an argument. Why is that?

Location class:

let locationManager = CLLocationManager()

public class Location {

    public func coordinate() -> (latitude: Float?, longitude: Float?) {
        let latitude = Float((locationManager.location?.coordinate.latitude)!)
        let longitude = Float((locationManager.location?.coordinate.longitude)!)

        return (latitude: latitude, longitude: longitude)
    }

    public func getCity() -> String {
        var returnCity: String = "N/A"
        let geoCoder = CLGeocoder()
        let location = CLLocation(latitude: (locationManager.location?.coordinate.latitude)!, longitude: (locationManager.location?.coordinate.longitude)!)

        geoCoder.reverseGeocodeLocation(location, completionHandler: { (placemarks, error) -> Void in
            // Place details
            var placeMark: CLPlacemark!
            placeMark = placemarks?[0]
            // City
            if let city = placeMark.addressDictionary!["City"] as? String {
                returnCity = city
            }
        })
        return returnCity
    }

    public func getCountry() -> String {
        var returnCountry: String = "N/A"
        let geoCoder = CLGeocoder()
        let location = CLLocation(latitude: (locationManager.location?.coordinate.latitude)!, longitude: (locationManager.location?.coordinate.longitude)!)

        geoCoder.reverseGeocodeLocation(location, completionHandler: { (placemarks, error) -> Void in
            // Place details
            var placeMark: CLPlacemark!
            placeMark = placemarks?[0]
            // City
            if let country = placeMark.addressDictionary!["Country"] as? String {
                returnCountry = country
            }
        })
        return returnCountry
    }

    public func getZip() -> Int {
        var returnZip: Int = 0
        let geoCoder = CLGeocoder()
        let location = CLLocation(latitude: (locationManager.location?.coordinate.latitude)!, longitude: (locationManager.location?.coordinate.longitude)!)

        geoCoder.reverseGeocodeLocation(location, completionHandler: { (placemarks, error) -> Void in
            // Place details
            var placeMark: CLPlacemark!
            placeMark = placemarks?[0]
            // City
            if let zip = placeMark.addressDictionary!["ZIP"] as? Int {
                returnZip = zip
            }
        })
        return returnZip
    }

    public func getLocationName() -> String {
        var returnName: String = "N/A"
        let geoCoder = CLGeocoder()
        let location = CLLocation(latitude: (locationManager.location?.coordinate.latitude)!, longitude: (locationManager.location?.coordinate.longitude)!)

        geoCoder.reverseGeocodeLocation(location, completionHandler: { (placemarks, error) -> Void in
            // Place details
            var placeMark: CLPlacemark!
            placeMark = placemarks?[0]
            // City
            if let locationName = placeMark.addressDictionary!["Name"] as? String {
                returnName = locationName
            }
        })
        return returnName
    }

    public func getStreetAddress() -> String {
        var returnAddress: String = "N/A"
        let geoCoder = CLGeocoder()
        let location = CLLocation(latitude: (locationManager.location?.coordinate.latitude)!, longitude: (locationManager.location?.coordinate.longitude)!)

        geoCoder.reverseGeocodeLocation(location, completionHandler: { (placemarks, error) -> Void in
            // Place details
            var placeMark: CLPlacemark!
            placeMark = placemarks?[0]
            // City
            if let street = placeMark.addressDictionary!["Thoroughfare"] as? String {
                returnAddress = street
            }
        })
        return returnAddress
    }
}

Trying to create a variable:

let city = Location.getCity()

Here are some screen shots of what I get:

回答1:

These methods are not class methods, they are instance methods. You must call them on an instance of the Location class, not on the class itself. Evidently, Swift can call instance methods similarly to Python: the method is a function owned by the class, and its argument is an instance of the class. But you should not call instance methods this way.

The best way to solve this problem is to construct a Location object and then call the method on it:

let city: Location = Location().getCity()

回答2:

Because you're trying to call it as a class function. You should be creating an instance of Location and calling the function on that. Note also that it returns String Where your code is telling the compiler you're expecting it to return a Location.