Xcode 16.2中WeatherKit.WeatherAlert新增成员无法编译访问问题

我使用Xcode Version 16.2 (16C5032a)和WeatherKit非REST API时遇到了一个问题：调试WeatherKit请求结果时，发现WeatherKit.WeatherAlert结构体除了metadata变量外，还新增了onsetTime、expirationDate、issuedDate、endDate几个直接成员（并非metadata的子成员）。但当我尝试在代码中直接访问这些成员时，Xcode会抛出编译错误：

WeatherAlert has no member 'onsetTime',...

而且苹果最新的官方文档中并未提及这些成员，有趣的是它们和WeatherKit REST API从一开始就提供的字段完全对应。

相关代码如下：

import Foundation
import WeatherKit
import CoreLocation

@available(iOS 16.0, *)
func queryWeather() {
    let location = CLLocation(latitude: 37.69300079345703, longitude: -97.33899688720703)
    Task.detached(priority: .userInitiated) {
        if let (alerts) = try? await WeatherService.shared.weather(for: location, including: .alerts),
           let alert = alerts.first
        {
            print(alert)
            print(alert.onsetTime) // 编译错误："Value of type 'WeatherAlert' has no member 'onsetTime'"

        }
    }
}

移除报错代码后程序可正常运行，print(alert)的输出中明确包含这些未公开的字段：

Optional(WeatherKit.WeatherAlert(detailsURL: https://weatherkit.apple.com/alertDetails/index.html?ids=3a1f2813-6f68-5186-b4c2-300811da2840&lang=en-GB&timezone=America/Chicago, source: "National Weather Service", date: 2025-02-19 16:03:10 +0000, expirationDate: 2025-02-20 00:00:00 +0000, issuedDate: 2025-02-19 08:46:00 +0000, onsetTime: Optional(2025-02-19 08:46:00 +0000), endDate: Optional(2025-02-20 18:00:00 +0000), summary: "Extreme Cold Warning", description: "Extreme Cold Warning", details: nil, region: nil, severity: severe, importance: High, metadata: WeatherKit.WeatherMetadata(date: 2025-02-19 16:03:10 +0000, expirationDate: 2025-02-19 16:08:10 +0000, latitude: 37.69300079345703, longitude: -97.33899688720703, attribution: Optional(WeatherKit.WeatherAttribution(storage: WeatherKit.WeatherAttribution.(unknown context at $1bee7afa8).Storage))), id: 3A1F2813-6F68-5186-B4C2-300811DA2840))

调试器的变量视图中也清晰显示这些字段的存在：

alerts  [WeatherKit.WeatherAlert]?  1 value
[0] WeatherKit.WeatherAlert 
    detailsURL          Foundation.URL  
    source              String  
    date                Foundation.Date
    expirationDate      Foundation.Date     
    issuedDate          Foundation.Date     
    onsetTime           Foundation.Date?    
    endDate             Foundation.Date?    
    summary             String
    description         String
    details             Foundation.URL? 
    region              String? 
    severity            WeatherKit.WeatherSeverity  
    importance          WeatherKit.WeatherImportance    
    metadata            WeatherKit.WeatherMetadata  
        date                Foundation.Date     
        expirationDate      Foundation.Date     
        latitude            Double  
        longitude           Double  
        attribution         WeatherKit.WeatherAttribution?
    id                  Foundation.UUID 

1. 用Swift反射（Mirror）安全访问未公开属性 #

可以通过Swift的Mirror机制读取这些未公开的属性，这种方式既不会触发编译错误，也能通过类型判断避免崩溃：

extension WeatherAlert {
    func getUndocumentedValue<T>(forKey key: String) -> T? {
        let mirror = Mirror(reflecting: self)
        for child in mirror.children {
            guard let childLabel = child.label, childLabel == key else {
                continue
            }
            return child.value as? T
        }
        return nil
    }
}

// 使用示例
if let onsetTime = alert.getUndocumentedValue(forKey: "onsetTime") as Date? {
    print("Onset Time: \(onsetTime)")
}

let expirationDate = alert.getUndocumentedValue(forKey: "expirationDate") as Date?
let issuedDate = alert.getUndocumentedValue(forKey: "issuedDate") as Date?
let endDate = alert.getUndocumentedValue(forKey: "endDate") as Date?

2. 关键注意事项 #

• 这种方法依赖苹果内部的属性命名，一旦苹果后续调整属性名称或移除这些字段，代码会直接失效，必须做好容错处理（比如默认值、空值判断）。
• 这些属于未公开API，苹果不提供官方支持，后续系统版本更新可能会变更或移除，不建议在核心生产逻辑中大规模依赖。

关于文档与API状态 #

目前苹果官方文档尚未更新这些字段的说明，推测是WeatherKit SDK内部提前添加了与REST API对齐的字段，但暂未开放正式访问权限。可以关注苹果开发者文档的后续更新，或者通过苹果开发者反馈渠道提交需求，建议官方正式开放这些属性的访问。

内容的提问来源于stack exchange，提问作者djmlewis