swift - 使用 URLSessionDownloadDelegate 获取 HTTP header

Question

我如何从服务器获取 header 以检查状态代码是 200、404 等？

我有一个委托(delegate)类:

class DownloadDelegate : NSObject, URLSessionDelegate, URLSessionDownloadDelegate, URLSessionTaskDelegate {
    // Implementations of delegate methods:
    [...]didFinishDownloadingTo location: URL[...]
    [...]didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64[...]
}

但我不确定在哪里可以提取 header 。

Answer 1

urlSession(_:downloadTask:didFinishDownloadingTo:)为您提供 header 。

参数 downloadTask 有一个类型为 URLResponse 的属性 .response .

假设您使用的是 HTTP/HTTPS，这可以转换为 HTTPURLResponse .

Whenever you make an HTTP request, the NSURLResponse object you get back is actually an instance of the HTTPURLResponse class.

(Source: API Reference of URLResponse)

HTTPURLResponse 具有获取状态代码 (statusCode) 和所有 header 字段的属性，如 [AnyHashable: Any] (allHeaderFields )。

示例:

func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
    guard let response = downloadTask.response as? HTTPURLResponse else {
        return //something went wrong
    }

    let status = response.statusCode
    let completeHeader = response.allHeaderFields
}