swift - Swift Ios13 上次修改日期函数

Question

我在挣扎……怎么了？“void 函数中出现意外的非 void 返回值”

非常感谢帮忙！！！

import Foundation

func lastmod() -> String {

    let url = URL(string: "https://www.url.de/pic1.png")
    let urlSession = URLSession.shared
    let task = urlSession.dataTask(with: url!) { (data, response, error) in
    guard let data = data, error == nil else {
        debugPrint("Fehler beim Laden von \(String(describing: url))", String(describing: error))
        return
    }
    if let response = response
        {
        let httpResponse = response as! HTTPURLResponse
        let str = String(describing: httpResponse.value(forHTTPHeaderField: "Last-Modified"))
        print(str)
        return str
        }
    }
    task.resume()
}

标签： swifthttpresponselast-modified