Question

在Linux上尝试使用Swift快速访问牛津词典api时，我发现了一个障碍。我正在做某些错误，但我无法确定它是什么。在这一点上，我怀疑与基本操作系统有关。因此，请考虑bash代码：

curl -X GET --header 'Accept: text/plain' --header 'app_id: 8a7dd147' --header 'app_key: 7e7d022fbce6d8d4523eac3baa5bd04c' 'https://od-api.oxforddictionaries.com/api/v1/entries/en/ace'

哪个返回单词Ace的json数据。现在，在Ubuntu 18.04上，我尝试以下操作：

import Foundation
//var request = URLRequest(url: URL(string: "https://od-api.oxforddictionaries.com/api/v1/entries/en/love")!)

// TODO: replace with your own app id and app key
let appId = "8a7dd147"
let appKey = "7e7d022fbce6d8d4523eac3baa5bd04c"
let language = "en"
let word = "Ace"
let word_id = word.lowercased() //word id is case sensitive and lowercase is required
let url = URL(string: "https://od-api.oxforddictionaries.com/api/v1/entries/en/love")!  // \(language)/\(word_id)")!
var request = URLRequest(url: url)
request.addValue("application/json", forHTTPHeaderField: "Accept")
request.addValue(appId, forHTTPHeaderField: "app_id")
request.addValue(appKey, forHTTPHeaderField: "app_key")
//request.addValue("application/json", forHTTPHeaderField: "Content-Type")
print("passed request addValue")

let session = URLSession.shared
_ = session.dataTask(with: request, completionHandler: { data, response, error in
    if let response = response,
        let data = data,
        let jsonData = try? JSONSerialization.jsonObject(with: data, options: .mutableContainers) {
            print("about to give you a response")
        print(response)
        print(jsonData)
    } else {
        print(error)
        print(NSString.init(data: data!, encoding: String.Encoding.utf8.rawValue))
    }
}).resume()

或以下内容：

import Foundation

let params: [String: String] = ["app_id": "8a7dd147", "app_key": "7e7d022fbce6d8d4523eac3baa5bd04c"]

var request = URLRequest(url: URL(string: "https://od-api.oxforddictionaries.com/api/v1/entries/en/love")!)
request.httpMethod = "GET"
request.addValue("application/json", forHTTPHeaderField: "Accept")
request.addValue("8a7dd147", forHTTPHeaderField: "app_id")
request.addValue("7e7d022fbce6d8d4523eac3baa5bd04c", forHTTPHeaderField: "app_key")

URLSession.shared.dataTask(with: request, completionHandler: { data, response, error -> Void in
    print(response!)
    do {
        let json = try JSONSerialization.jsonObject(with: data!)
        print(json)
        print("we did it!")
    } catch {
        print("error")
    }
}).resume()

//task.resume()

但是没有人返回单词“ love”的json信息。我一直在尝试调试它，无法弄清楚出了什么问题。

它与操作系统相关，因此是错误吗？有人可以在MacOS上对其进行测试。还是我想念什么？

Answer 1

URLSession在后台线程上执行操作。并且当您结束多线程程序的主线程时，所有线程都被终止（除了在Java之类的某些语言中，您可以设置Daemon线程，该线程可能是其他线程，但是在该程序结束之后才结束程序）线程）。

因此，您的解决方案是延长主线程的生命周期，例如：

let group = DispatchGroup.init()

group.enter() // Use this before making anything that needs to be waited for
              // This manually add one to operation count in the dispatch group
URLSession.shared.dataTask(with: request, completionHandler: { data, response, error -> Void in
    defer {  // Defer makes all ends of this scope make something, here we want to leave the dispatch.
             // This is executed when the scope ends, even if with exception.


       group.leave() // Manually subtract one from the operation count
    }
    print(response!)
    do {
        let json = try JSONSerialization.jsonObject(with: data!)
        print(json)
        print("we did it!")
    } catch {
        print("error")
    }
}).resume()

group.wait()  // Wait for group to end operations.

但是更好的是，您不会阻塞现实生活中的应用程序（例如，Web应用程序）中的主线程，因此您的应用程序通常比请求的寿命更长，因此您无需进行干预，但尽量避免阻止用户（sleep，DispatchGroup.wait阻止用户，除非在后台线程中，等等。）

Answer 2

您也可以使用以下代码：

// Avoid closing this project for 40 seconds
RunLoop.main.run(until: Date(timeIntervalSinceNow: 40))

Linux上是否支持URLSession？

2 个答案: