使用组合的 Swift HTTP POST 请求

Question

在我的应用程序中，我使用 Combine 框架发出网络请求，它适用于 GET 请求。但我在 POST 请求中遇到了这个问题。

以下代码（没有合并）可以正常工作：

let data = ["statusTime": DateFormatter.iso8601Full.string(from: Date())]
let requestBody = try? JSONSerialization.data(withJSONObject: data, options: [])
let baseURL = "my-api.amazonaws.com"
let endpoint = "/my/endpoint"

var urlComponents = URLComponents()
urlComponents.scheme = "https"
urlComponents.host = baseURL
urlComponents.path = endpoint
let url = urlComponents.url!
var request = URLRequest(url: url)

request.httpMethod = "POST"
request.httpBody = requestBody

request.addValue(authorizationToken, forHTTPHeaderField: "Authorization")
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")

let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
    if let error = error {
        print("error: \(error)")
        return
    }
    print("Response: \((response as! HTTPURLResponse).statusCode)")
}
task.resume()

我从上面的代码中得到一个 200 响应代码。

与 Combine 相同的代码：

let data = ["statusTime": DateFormatter.iso8601Full.string(from: Date())]
let requestBody = try? JSONSerialization.data(withJSONObject: data, options: [])
let baseURL = "my-api.amazonaws.com"
let endpoint = "/my/endpoint"

var urlComponents = URLComponents()
urlComponents.scheme = "https"
urlComponents.host = baseURL
urlComponents.path = endpoint
let url = urlComponents.url!
var request = URLRequest(url: url)

request.httpMethod = "POST"
request.httpBody = requestBody

request.addValue(authorizationToken, forHTTPHeaderField: "Authorization")
request.addValue("application/json", forHTTPHeaderField: "Content-Type")
request.addValue("application/json", forHTTPHeaderField: "Accept")

let cancellable = URLSession.shared
    .dataTaskPublisher(for: request)
    .print()
    .sink(receiveCompletion: {
        if let error = $0.error {
            print("Failure: \(error)")
        }
    }, receiveValue: {
        print("\($0)")
    })

这是我收到的输出：

receive subscription: (DataTaskPublisher)
request unlimited
receive cancel

似乎使用 Combine 框架的请求以某种方式被取消了？我使用了一个网络跟踪应用程序，我可以看到第一个请求（没有合并），但看不到第二个请求。

我查看了许多帖子和文档，但看不出我的代码有什么问题。我错过了什么？提前致谢。

Answer 1

我看到您正在创建cancellable，但您是否对它进行了强烈引用？看起来您正在创建请求，然后可取消对象超出范围并被释放，从而取消了请求。

在你的课堂上声明这样的事情：

var cancellables = Set<AnyCancellable>()

然后您将可取消的内容隐式存储为：

URLSession.shared // You don't hold on to the returned cancellable here
    .dataTaskPublisher(for: request)
    .print()
    .sink(receiveCompletion: {
        if let error = $0.error {
            print("Failure: \(error)")
        }
    }, receiveValue: {
        print("\($0)")
    })
    .store(in: &cancellables) // This puts the cancellable into the variables so it stays in scope