iOS开发：WebService完成后执行Segue及AsyncTask等效方案问询

嗨，作为iOS开发新手，我完全理解你想找类似Android AsyncTask的异步处理方案的需求～在iOS生态里并没有直接对应的AsyncTask，但有几种更贴合iOS开发习惯的异步处理方式，刚好能解决你网络请求完成后传递数据到下一个视图控制器的问题，我结合你的代码片段给你详细拆解：

1. 闭包（Closure）+ URLSession（最基础通用，兼容全iOS版本） #

这是iOS开发中最常用的异步处理方式，核心是通过闭包回调获取异步请求的结果，再进行页面跳转和数据传递。

首先你需要改造FlightWebService的getFlightData方法，把它从同步逻辑改成带闭包回调的异步网络请求：

class FlightWebService {
    // 定义闭包回调，用Result类型统一处理成功/失败
    func getFlightData(airportCode: String, minutesBefore: String, minutesAfter: String, completion: @escaping (Result<[Flight], Error>) -> Void) {
        // 替换成你的实际接口地址
        guard let url = URL(string: "https://your-api-url.com/flights?airport=\(airportCode)&before=\(minutesBefore)&after=\(minutesAfter)") else {
            completion(.failure(NSError(domain: "InvalidURL", code: -1, userInfo: [NSLocalizedDescriptionKey: "无效的请求地址"])))
            return
        }
        
        // 发起异步网络请求
        let task = URLSession.shared.dataTask(with: url) { data, response, error in
            // 先处理请求错误
            if let error = error {
                completion(.failure(error))
                return
            }
            
            // 校验返回数据
            guard let responseData = data else {
                completion(.failure(NSError(domain: "NoData", code: -2, userInfo: [NSLocalizedDescriptionKey: "未获取到数据"])))
                return
            }
            
            // 解析JSON数据到你的Flight模型
            do {
                let flights = try JSONDecoder().decode([Flight].self, from: responseData)
                completion(.success(flights))
            } catch {
                completion(.failure(error))
            }
        }
        task.resume()
    }
}

然后在你的视图控制器中调用这个方法，拿到数据后跳转页面：

@IBAction func searchAction(_ sender: Any) {
    // 先校验输入合法性（避免强制解包崩溃）
    guard let airportName = airportCode.text, !airportName.isEmpty,
          let minutesBefore = minutesBehind.text, !minutesBefore.isEmpty,
          let minutesAfter = minutesAhead.text, !minutesAfter.isEmpty else {
        // 输入为空时弹提示
        let alert = UIAlertController(title: "提示", message: "请填写完整信息", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "确定", style: .default))
        present(alert, animated: true)
        return
    }
    
    // 发起网络请求
    FlightWebService().getFlightData(airportCode: airportName, minutesBefore: minutesBefore, minutesAfter: minutesAfter) { [weak self] result in
        // 网络请求在后台线程，必须切回主线程处理UI操作（跳转页面属于UI操作）
        DispatchQueue.main.async {
            switch result {
            case .success(let flights):
                // 跳转到下一个视图控制器并传递数据
                let nextVC = FlightListViewController() // 替换成你的目标VC类名
                nextVC.flightData = flights // 假设目标VC有接收数据的属性
                self?.navigationController?.pushViewController(nextVC, animated: true)
                // 如果是模态跳转：self?.present(nextVC, animated: true)
                
            case .failure(let error):
                // 处理请求失败的情况
                let alert = UIAlertController(title: "请求失败", message: error.localizedDescription, preferredStyle: .alert)
                alert.addAction(UIAlertAction(title: "确定", style: .default))
                self?.present(alert, animated: true)
            }
        }
    }
}

注意：用[weak self]是为了避免循环引用，防止内存泄漏；所有UI操作必须在主线程执行，所以要用DispatchQueue.main.async切换线程。

2. Async/Await（iOS 15+，Swift 5.5+，代码更简洁） #

如果你的项目支持iOS 15及以上版本，Async/Await是更优雅的选择，它让异步代码看起来像同步代码，可读性更强。

先改造FlightWebService的方法：

class FlightWebService {
    func getFlightData(airportCode: String, minutesBefore: String, minutesAfter: String) async throws -> [Flight] {
        guard let url = URL(string: "https://your-api-url.com/flights?airport=\(airportCode)&before=\(minutesBefore)&after=\(minutesAfter)") else {
            throw NSError(domain: "InvalidURL", code: -1, userInfo: [NSLocalizedDescriptionKey: "无效的请求地址"])
        }
        
        // 用async/await发起请求
        let (data, response) = try await URLSession.shared.data(from: url)
        
        // 校验HTTP响应状态
        guard let httpResponse = response as? HTTPURLResponse, httpResponse.statusCode == 200 else {
            throw NSError(domain: "InvalidResponse", code: -3, userInfo: [NSLocalizedDescriptionKey: "服务器响应异常"])
        }
        
        // 解析数据
        return try JSONDecoder().decode([Flight].self, from: data)
    }
}

然后修改你的searchAction方法为异步方法：

@IBAction func searchAction(_ sender: Any) async {
    guard let airportName = airportCode.text, !airportName.isEmpty,
          let minutesBefore = minutesBehind.text, !minutesBefore.isEmpty,
          let minutesAfter = minutesAhead.text, !minutesAfter.isEmpty else {
        let alert = UIAlertController(title: "提示", message: "请填写完整信息", preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "确定", style: .default))
        present(alert, animated: true)
        return
    }
    
    do {
        // 异步获取数据
        let flights = try await FlightWebService().getFlightData(airportCode: airportName, minutesBefore: minutesBefore, minutesAfter: minutesAfter)
        
        // 跳转页面（保险起见切回主线程）
        DispatchQueue.main.async {
            let nextVC = FlightListViewController()
            nextVC.flightData = flights
            self.navigationController?.pushViewController(nextVC, animated: true)
        }
    } catch {
        // 处理错误
        DispatchQueue.main.async {
            let alert = UIAlertController(title: "请求失败", message: error.localizedDescription, preferredStyle: .alert)
            alert.addAction(UIAlertAction(title: "确定", style: .default))
            self.present(alert, animated: true)
        }
    }
}

3. Combine框架（iOS 13+，响应式编程） #

如果你需要处理复杂的数据流场景（比如多个异步请求联动、实时数据更新），Combine框架是个不错的选择，它属于响应式编程范畴。

先改造FlightWebService：

import Combine

class FlightWebService {
    func getFlightData(airportCode: String, minutesBefore: String, minutesAfter: String) -> AnyPublisher<[Flight], Error> {
        guard let url = URL(string: "https://your-api-url.com/flights?airport=\(airportCode)&before=\(minutesBefore)&after=\(minutesAfter)") else {
            return Fail(error: NSError(domain: "InvalidURL", code: -1, userInfo: [NSLocalizedDescriptionKey: "无效的请求地址"])).eraseToAnyPublisher()
        }
        
        // 用Combine的dataTaskPublisher发起请求
        return URLSession.shared.dataTaskPublisher(for: url)
            .map(\.data) // 提取返回的数据
            .decode(type: [Flight].self, decoder: JSONDecoder()) // 解析数据
            .eraseToAnyPublisher() // 隐藏内部实现细节
    }
}

然后在视图控制器中使用Combine：

import Combine

class YourViewController: UIViewController {
    // 用来管理Combine订阅，防止内存泄漏
    private var cancellables = Set<AnyCancellable>()

    @IBAction func searchAction(_ sender: Any) {
        guard let airportName = airportCode.text, !airportName.isEmpty,
              let minutesBefore = minutesBehind.text, !minutesBefore.isEmpty,
              let minutesAfter = minutesAhead.text, !minutesAfter.isEmpty else {
            let alert = UIAlertController(title: "提示", message: "请填写完整信息", preferredStyle: .alert)
            alert.addAction(UIAlertAction(title: "确定", style: .default))
            present(alert, animated: true)
            return
        }
        
        FlightWebService().getFlightData(airportCode: airportName, minutesBefore: minutesBefore, minutesAfter: minutesAfter)
            .receive(on: DispatchQueue.main) // 切换到主线程处理结果
            .sink(
                receiveCompletion: { [weak self] completion in
                    if case .failure(let error) = completion {
                        let alert = UIAlertController(title: "请求失败", message: error.localizedDescription, preferredStyle: .alert)
                        alert.addAction(UIAlertAction(title: "确定", style: .default))
                        self?.present(alert, animated: true)
                    }
                },
                receiveValue: { [weak self] flights in
                    let nextVC = FlightListViewController()
                    nextVC.flightData = flights
                    self?.navigationController?.pushViewController(nextVC, animated: true)
                }
            )
            .store(in: &cancellables) // 保存订阅到cancellables中
    }
}

总结 #

• 如果你需要兼容低版本iOS（比如iOS 12及以下），优先选择闭包+URLSession的方案；
• 如果项目支持iOS 15+，Async/Await是最简洁易读的选择，推荐新手学习；
• 如果有复杂的数据流需求，再考虑Combine框架。

内容的提问来源于stack exchange，提问作者Ackman