Question

我正在尝试使用新的Combine框架解析JSON。但是，我所做的每一次尝试都会返回一个已取消的错误。当我使用完全相同的网址而不结合使用时，效果很好。

底部功能正常，顶部功能无论执行什么操作都会给我一个错误。

static func performNetworkRequestUsingCombine(url urlWithQuery:URL){
        //let decoder = JSONDecoder()
        let publisher = URLSession.shared.dataTaskPublisher(for: urlWithQuery)
            .map({$0.data})

        .eraseToAnyPublisher()
            .sink(receiveCompletion: { (status) in
                switch status {
                    case .failure(let incomingError):
                        print(incomingError.localizedDescription)
                    case .finished:
                    break
                }
            }) { (data) in
                let dataString = String(data: data, encoding: .utf8)
                print(dataString!)
        }
        publisher.cancel()
    }

static func performNetworkRequest(url urlWithQuery: URL, dataValue : @escaping (WeatherObject)->Void){

        let decoder = JSONDecoder()
        let task = URLSession.shared.dataTask(with: urlWithQuery) { (data, response, error) in

            if error != nil {
                print(error!.localizedDescription)
                return
            }
            if let data = data {
                do {
                    let weatherData = try decoder.decode(WeatherObject.self, from: data)
                    dataValue(weatherData)
                } catch let localError {
                    print(localError.localizedDescription)
                }
            }
        }
        task.resume()
    }

}

我希望收到在终端上打印的JSON数据，但是却收到以下错误：

2019-10-25 14：59：34.452071-0400 Clima [2127：98883]任务<663D6D3A-48B8-49E6-9103-AA1D89513D84>。<1>完成，错误为[-999]错误域= NSURLErrorDomain代码= -999“已取消” UserInfo = {NSErrorFailingURLStringKey = https://api.openweathermap.org/data/2.5/weather?lon=-122.4&APPID=29ecd35ff6b9e63498cb8fb479ba6ca0&units=imperial&lat=37.8，NSLocalizedDescription =已取消，NSErrorFailingURLKey = https://api.openweathermap.org/data/2.5/weather?lon=-122.4&APPID=29ecd35ff6b9e63498cb8fb479ba6ca0&units=imperial&lat=37.8}

Answer 1

添加了.receive（on :)运算符，从而解决了该问题！

static func performNetworkRequestUsingCombine(url urlWithQuery:URL){
        //let decoder = JSONDecoder()

        let publisher = URLSession.shared.dataTaskPublisher(for: urlWithQuery)
            .map({$0.data})
            .receive(on: DispatchQueue.main)
            .sink(receiveCompletion: { (completionError) in
                switch completionError {
                    case .failure(let error):
                        print(error.localizedDescription)
                    case .finished:
                    break
                }
            }) { (data) in
                guard let stringData = String(data: data, encoding: .utf8) else {return}
                print(stringData)
        }
        publisher.cancel()
    }

Answer 2

只是停止取消您的订户人。删除publisher.cancel()。这是什么问题？

如何解决-合并错误|错误域= NSURLErrorDomain代码= -999“已取消”

2 个答案: