ios - iOS get file size before downloading

Question

I couldn't find a solution that worked for me. But I need to get the file size of a video I am downloading so that I can make sure the user has enough space on his phone for it.

My thoughts are to check the size of the video, then if the user has space for it, I would download it. Any recommendations?

NSURL *url = [NSURL URLWithString:stringURL];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
NSURLSession *session = [NSURLSession sharedSession];

NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithRequest:request completionHandler:^(NSURL *location, NSURLResponse *response, NSError *error) {...}];

Answer 1

这是其他答案的变体，它使用函数（在 Swift 4 中）在检索大小时调用闭包：

func getDownloadSize(url: URL, completion: @escaping (Int64, Error?) -> Void) {
    let timeoutInterval = 5.0
    var request = URLRequest(url: url,
                             cachePolicy: .reloadIgnoringLocalAndRemoteCacheData,
                             timeoutInterval: timeoutInterval)
    request.httpMethod = "HEAD"
    URLSession.shared.dataTask(with: request) { (data, response, error) in
        let contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
        completion(contentLength, error)
    }.resume()
}

以下是如何使用此功能：

let url = URL(string: "https://upload.wikimedia.org/wikipedia/commons/7/70/Example.png")!
getDownloadSize(url: url, completion: { (size, error) in
    if error != nil {
        print("An error occurred when retrieving the download size: \(error.localizedDescription)")
    } else {
        print("The download size is \(size).")
    }
})

Answer 2

Swift 3： 由于您正在调用 dataTask ，因此您不能在块之外使用该值，因此请以这种方式使用它。

 var contentLength: Int64 = NSURLSessionTransferSizeUnknown
                let request = NSMutableURLRequest(url: url as URL, cachePolicy: NSURLRequest.CachePolicy.reloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 30.0);
                request.httpMethod = "HEAD";
                request.timeoutInterval = 5;
                let group = DispatchGroup()
                group.enter()
                URLSession.shared.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
                    contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
//Here you should use the value
                    print("contentLength",contentLength)
                    group.leave()
                }).resume()

Answer 3

使用此函数获取 URL 的远程大小。请注意这个函数是同步的并且会阻塞线程，所以从不同于主线程的线程调用它：

extension NSURL {
    var remoteSize: Int64 {
        var contentLength: Int64 = NSURLSessionTransferSizeUnknown
        let request = NSMutableURLRequest(URL: self, cachePolicy: NSURLRequestCachePolicy.ReloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 30.0);
        request.HTTPMethod = "HEAD";
        request.timeoutInterval = 5;
        let group = dispatch_group_create()
        dispatch_group_enter(group)
        NSURLSession.sharedSession().dataTaskWithRequest(request, completionHandler: { (data, response, error) -> Void in
            contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
            dispatch_group_leave(group)
        }).resume()
        dispatch_group_wait(group, dispatch_time(DISPATCH_TIME_NOW, Int64(5 * NSEC_PER_SEC)))
        return contentLength
    }
}

然后在与主线程不同的线程上随处调用 remoteSize 变量：

let size = url.remoteSize

Answer 4

斯威夫特 3：

extension NSURL {
    var remoteSize: Int64 {
        var contentLength: Int64 = NSURLSessionTransferSizeUnknown
        let request = NSMutableURLRequest(url: self as URL, cachePolicy: NSURLRequest.CachePolicy.reloadIgnoringLocalAndRemoteCacheData, timeoutInterval: 30.0);
        request.httpMethod = "HEAD";
        request.timeoutInterval = 5;
        let group = DispatchGroup()
        group.enter()
        URLSession.shared.dataTask(with: request as URLRequest, completionHandler: { (data, response, error) -> Void in
            contentLength = response?.expectedContentLength ?? NSURLSessionTransferSizeUnknown
            group.leave()
        }).resume()

        return contentLength
    }
}