没有参数的方法是调用参数 [英] A method without parameters is calling for an argument

问题描述

我有一个名为 Location 的类，它有几个没有任何参数的方法。

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

然而，当我尝试创建一个变量与方法的结果，它想要一个参数。为什么呢？

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

位置 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
    }
}

尝试创建一个变量：

let city = Location.getCity()

这里是我得到的一些屏幕截图：

Here are some screen shots of what I get:

推荐答案

这些方法不是类方法，它们是实例方法。您必须在 Location 类的实例上调用它们，而不是类本身。显然，Swift可以类似于Python调用实例方法：该方法是该类拥有的函数，其参数是类的一个实例。但是你不应该这样调用实例方法。

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.

解决这个问题的最好方法是构造一个 Location 对象，然后调用其上的方法：

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()

这篇关于没有参数的方法是调用参数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！