swift - 枚举数组时获取 header

Question

我尝试获取有关 url 位于数组中的远程文件的 header 信息。我的获取 header 的函数在单独调用时可以完美运行，但在数组枚举内部时则无法运行。这是我的功能:

    func getHeaderInformations (myUrl: URL, completion: @escaping (_ content: String?) -> ()) {
    var request = URLRequest(url: myUrl)
    request.httpMethod = "HEAD"
    let task = URLSession.shared.dataTask(with: request) { (data, response, error) in
        guard error == nil, let reponse = response as? HTTPURLResponse, let contentType = reponse.allHeaderFields["Content-Type"],let contentLength = reponse.allHeaderFields["Content-Length"]

            else{
                completion(nil)
                return
        }
        let content = String(describing: contentType) + "/" + String(describing: contentLength)

        completion(content)
    }
    task.resume()
}

    // download picture
func downloadPic (){
    let minimumSize=UserDefaults.standard.object(forKey: "Minimum_size") as! Int64
    var imgExtension:String=""
    var type:String=""
    var size:Int64=0

    for (_,item) in LiensImgArrayURL.enumerated() {
        getHeaderInformations(myUrl: item, completion: { content in
           let myInfoArray = content?.components(separatedBy: "/")
            type=(myInfoArray?[0])!
            imgExtension=(myInfoArray?[1])!
            size=Int64((myInfoArray?[2])!)!
        })
        if (type=="image" && size>=minimumSize) {
            SaveFileToDirectory(myRemoteUrl: item, myExtension: imgExtension)
        }
        }
}

我怎样才能写好这段“getHeaderInformations”代码，并在函数“downLoadPic”中返回好的值？

感谢您的回答...

Answer 1

由于 getHeaderInformations 异步工作，因此将代码保存在闭包中中。

如果您不需要 for 循环中的索引，则也不需要 enumerated()。

我调整了代码，去掉了丑陋的问号、感叹号和括号。

for item in LiensImgArrayURL {
    getHeaderInformations(myUrl: item, completion: { content in
       if let myInfoArray = content?.components(separatedBy: "/") {
            type = myInfoArray[0]
            imgExtension = myInfoArray[1]
            size = Int64(myInfoArray[2])!
            if type == "image" && size >= minimumSize {
                SaveFileToDirectory(myRemoteUrl: item, myExtension: imgExtension)
            }
       }
    })
}