当其中一个属性是通过 API 调用获得的另外两个属性计算出来时，如何填充模型属性？

Question

[已解决]

我没有将

reverseGeocode

视为异步函数，导致计时问题和数据无法正确填充。使用

async await

解决了这个问题。

解决方案：

func getCurrentWeather(latitude: CLLocationDegrees, longitude: CLLocationDegrees) async throws -> WeatherReport? {
        do {
            guard let url = URL(string: "https://api.openweathermap.org/data/3.0/onecall?lat=\(latitude)&lon=\(longitude)&exclude=current,minutely,hourly, alerts&appid=19054ace749a2f641842133743dfdfd9&units=imperial") else { throw NetworkError.badURL}
            
            let (data, response) = try await URLSession.shared.data(from: url)
            
            guard let response = response as? HTTPURLResponse else { throw NetworkError.badResponse }
            guard response.statusCode >= 200 && response.statusCode < 300 else { throw NetworkError.badStatus }
            
            let decodedData = try JSONDecoder().decode(WeatherReport.self, from: data)
            let decodedDataWithCity = try await decodedData.reverseGeocode()
            return decodedDataWithCity
            
        } catch NetworkError.badURL {
            print("Error creating URL")
        } catch NetworkError.badResponse {
            print("Didn't get a valid response")
        } catch NetworkError.badStatus {
            print("Didn't get a 2xx status code from response")
        } catch {
            print("An error occurred downloading the data")
        }
        
        return nil
    }

func reverseGeocode() async throws -> WeatherReport? {
        let geocoder = CLGeocoder()
        let location = CLLocation(latitude: lat, longitude: lon)
        var report: WeatherReport?
        
        do {
            let placemarks = try await geocoder.reverseGeocodeLocation(location)
            let placemark = placemarks.first
            report = WeatherReport(lat: lat, lon: lon, city: placemark?.locality, timezone: timezone, timezoneOffset: timezoneOffset, daily: daily)
        } catch {
            print("Error: \(error.localizedDescription)")
        }
        
        return report
    }

func getCurrentWeather(latitude: CLLocationDegrees, longitude: CLLocationDegrees) async throws -> WeatherReport? {
        do {
            guard let url = URL(string: "https://api.openweathermap.org/data/3.0/onecall?lat=\(latitude)&lon=\(longitude)&exclude=current,minutely,hourly, alerts&appid=19054ace749a2f641842133743dfdfd9&units=imperial") else { throw NetworkError.badURL}
            
            let (data, response) = try await URLSession.shared.data(from: url)
            
            guard let response = response as? HTTPURLResponse else { throw NetworkError.badResponse }
            guard response.statusCode >= 200 && response.statusCode < 300 else { throw NetworkError.badStatus }
            
            let decodedData = try JSONDecoder().decode(WeatherReport.self, from: data)
            let decodedDataWithCity = decodedData.reverseGeocode(latitude: decodedData.lat, longitude: decodedData.lon)
            return decodedDataWithCity
            
        } catch NetworkError.badURL {
            print("Error creating URL")
        } catch NetworkError.badResponse {
            print("Didn't get a valid response")
        } catch NetworkError.badStatus {
            print("Didn't get a 2xx status code from response")
        } catch {
            print("An error occurred downloading the data")
        }
        
        return nil
    }

[原帖]

我正在构建一个简单的天气应用程序，它显示：

用户的城市名称（这部分有问题）
当前温度
每日最低/最高温度
风速
湿度

OpenWeatherMap API 提供除城市名称之外的所有数据，但我很难弄清楚获取它的逻辑流程。

我当前（失败）的方法是：

WeatherReport

 的模型，其中包含天气预报的所有属性。

struct WeatherReport: Codable {
    var lat, lon: Double
    var city: String?
    let timezone: String
    let timezoneOffset: Int
    let daily: [Daily]

city

 作为可选，因为调用填充这些属性的 API 将不会返回城市名称。

city

 通过反向地理编码确定的计算属性（提供纬度、经度和返回位置名称）。

func getCurrentWeather(latitude: CLLocationDegrees, longitude: CLLocationDegrees) async throws -> WeatherReport? {
        do {
            guard let url = URL(string: "https://api.openweathermap.org/data/3.0/onecall?lat=\(latitude)&lon=\(longitude)&exclude=current,minutely,hourly, alerts&appid=19054ace749a2f641842133743dfdfd9&units=imperial") else { throw NetworkError.badURL}
            
            let (data, response) = try await URLSession.shared.data(from: url)
            
            guard let response = response as? HTTPURLResponse else { throw NetworkError.badResponse }
            guard response.statusCode >= 200 && response.statusCode < 300 else { throw NetworkError.badStatus }
            
            let decodedData = try JSONDecoder().decode(WeatherReport.self, from: data)
            return decodedData
            
        } catch NetworkError.badURL {
            print("Error creating URL")
        } catch NetworkError.badResponse {
            print("Didn't get a valid response")
        } catch NetworkError.badStatus {
            print("Didn't get a 2xx status code from response")
        } catch {
            print("An error occurred downloading the data")
        }
        
        return nil
    }

（这就是我遇到所有麻烦的地方）

city
```
 属性。
```

尝试#1

reverseGeocode

 函数，该函数采用纬度/经度 (CLLocationDegrees) 并返回城市名称（字符串）。

didSet

 属性观察器调用

reverseGeocode

 函数来计算

city

失败是因为

'var' declarations with multiple variables cannot have explicit getters/setters

var lat, lon: Double {
        didSet {
            self.city = reverseGeocode(latitude: lat, longitude: lon)
        }
    }

func reverseGeocode(latitude: CLLocationDegrees, longitude: CLLocationDegrees) -> String {
        let geocoder = CLGeocoder()
        let location = CLLocation(latitude: latitude, longitude: longitude)
        var cityName: String
        
        geocoder.reverseGeocodeLocation(location) { placemarks, error in
            print("in geocoder.reverseGeocodeLocation function")
            // ensure no error
            guard error == nil else { return }
            
            // ensure there are placemarks
            if let placemarks = placemarks,
               let placemark = placemarks.first {
                cityName = placemark.locality ?? "Current location"
            }
        }
        
        return cityName
    }

尝试＃2

reverseGeocode
```
 方法以返回 
```
WeatherReport
```
 而不是 
```
String

WeatherReport

（不包括城市名称） - 我们调用

reverseGeocode

 方法来生成包含城市名称的新

WeatherReport

。

失败，因为它挂在获取

WeatherReport

 来生成视图的异步任务上。最初认为

reverseGeocode

 方法不起作用，但在其中添加了一些打印语句来确认它是有效的。

在等待

WeatherReport

 进入时，视图卡在加载旋转器上。

@EnvironmentObject private var locationManager: LocationManager
private let weatherManager = WeatherManager()
@State var weatherReport: WeatherReport?

var body: some View {
        ZStack {
            // if location exists...
            if let location = locationManager.location {
                // ..and weather report exists
                if let weatherReport = weatherReport {
                    // show WeatherView
                    WeatherView(weatherReport: weatherReport)
                } else {
                    // show loading spinner
                    LoadingView()
                        .task {
                            do {
                                // obtain weather report
                                weatherReport = try await weatherManager.getCurrentWeather(latitude: location.latitude, longitude: location.longitude)
                            } catch {
                                print("Unable to get weather info - Error: \(error.localizedDescription)")
                            }
                        }
                }

func getCurrentWeather(latitude: CLLocationDegrees, longitude: CLLocationDegrees) async throws -> WeatherReport? {
        do {
            guard let url = URL(string: "https://api.openweathermap.org/data/3.0/onecall?lat=\(latitude)&lon=\(longitude)&exclude=current,minutely,hourly, alerts&appid=19054ace749a2f641842133743dfdfd9&units=imperial") else { throw NetworkError.badURL}
            
            let (data, response) = try await URLSession.shared.data(from: url)
            
            guard let response = response as? HTTPURLResponse else { throw NetworkError.badResponse }
            guard response.statusCode >= 200 && response.statusCode < 300 else { throw NetworkError.badStatus }
            
            let decodedData = try JSONDecoder().decode(WeatherReport.self, from: data)
            let decodedDataWithCity = decodedData.reverseGeocode(latitude: decodedData.lat, longitude: decodedData.lon)
            return decodedDataWithCity
            
        } catch NetworkError.badURL {
            print("Error creating URL")
        } catch NetworkError.badResponse {
            print("Didn't get a valid response")
        } catch NetworkError.badStatus {
            print("Didn't get a 2xx status code from response")
        } catch {
            print("An error occurred downloading the data")
        }
        
        return nil
    }

func reverseGeocode(latitude: CLLocationDegrees, longitude: CLLocationDegrees) -> WeatherReport {
        let geocoder = CLGeocoder()
        let location = CLLocation(latitude: latitude, longitude: longitude)
        var report: WeatherReport
        
        geocoder.reverseGeocodeLocation(location) { placemarks, error in
            print("in geocoder.reverseGeocodeLocation function")
            // ensure no error
            guard error == nil else { return }
            
            // ensure there are placemarks
            if let placemarks = placemarks,
               let placemark = placemarks.first {
                report = WeatherReport(lat: lat, lon: lon, city: placemark.locality, timezone: timezone, timezoneOffset: timezoneOffset, daily: daily)
                print("report: \(report)")
            }
        }
        
        return report
    }

对于其他上下文，这是我正在尝试构建的视图。任何帮助将不胜感激，谢谢！

Answer 1

您可以制作一个

CityView

，例如

struct CityView: View {
    @Environment(\.myGeocoder) var myGeocoder
    let lat, lon: Double
    @State var city: City?

    var body: some View {
        Text(city.name ?? "Loading...")
        .task(id: [lat, lon]) {
            do {
                self.city = try await myGeocoder.reverseGeocode(latitude: lat, longitude: lon)
            }
            catch {
                print(error.localizedDescription)
        }
    }
}

当其中一个属性是通过 API 调用获得的另外两个属性计算出来时，如何填充模型属性？

问题描述投票：0回答：1

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当其中一个属性是通过 API 调用获得的另外两个属性计算出来时，如何填充模型属性？

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