迅速にファイルをダウンロードする方法は？

Question

Androidから来るiOS向けのApple Swiftプログラミングの学習を始めました。基本的にSwiftコードを読み取って操作できるようになり、iOS Swiftプログラミングで使用されるいくつかの一般的なクラスを学びましたが、それでも構文やすべてに混乱があります。

ファイルをダウンロードしようとしています。のように、このURLから来たと言ってみましょう

var url = "http://www.mywebsite.com/myfile.pdf"

ボタンをクリックします。たぶん視覚的な進歩も

ここでstackoverflowを検索して、Alamofireを見つけました。私はそれを試すかもしれませんが、これが私にとってそれが最善の方法であるかどうかはわかりません。

それで、目標を達成するためのオプション（iOS7およびiOS8）をどのように、どのように選択するかを尋ねたいと思います。また、長所と短所は素晴らしいでしょう！

Answer 1

Alamofireを使用しないダウンローダークラスの例：

class Downloader {
    class func load(URL: NSURL) {
        let sessionConfig = NSURLSessionConfiguration.defaultSessionConfiguration()
        let session = NSURLSession(configuration: sessionConfig, delegate: nil, delegateQueue: nil)
        let request = NSMutableURLRequest(URL: URL)
        request.HTTPMethod = "GET"
        let task = session.dataTaskWithRequest(request, completionHandler: { (data: NSData!, response: NSURLResponse!, error: NSError!) -> Void in
            if (error == nil) {
                // Success
                let statusCode = (response as NSHTTPURLResponse).statusCode
                println("Success: \(statusCode)")

                // This is your file-variable:
                // data
            }
            else {
                // Failure
                println("Failure: %@", error.localizedDescription);
            }
        })
        task.resume()
    }
}

これはあなた自身のコードでそれを使用する方法です：

class Foo {
    func bar() {
        if var URL = NSURL(string: "http://www.mywebsite.com/myfile.pdf") {
            Downloader.load(URL)
        }
    }
}

Swift 3バージョン

また、代わりにメモリではなくディスクに大きなファイルをダウンロードすることにも注意してください。 `downloadTask：を参照してください。

class Downloader {
    class func load(url: URL, to localUrl: URL, completion: @escaping () -> ()) {
        let sessionConfig = URLSessionConfiguration.default
        let session = URLSession(configuration: sessionConfig)
        let request = try! URLRequest(url: url, method: .get)

        let task = session.downloadTask(with: request) { (tempLocalUrl, response, error) in
            if let tempLocalUrl = tempLocalUrl, error == nil {
                // Success
                if let statusCode = (response as? HTTPURLResponse)?.statusCode {
                    print("Success: \(statusCode)")
                }

                do {
                    try FileManager.default.copyItem(at: tempLocalUrl, to: localUrl)
                    completion()
                } catch (let writeError) {
                    print("error writing file \(localUrl) : \(writeError)")
                }

            } else {
                print("Failure: %@", error?.localizedDescription);
            }
        }
        task.resume()
    }
}

Answer 2

次に、同期と非同期の実行方法を示す例を示します。

import Foundation

class HttpDownloader {

    class func loadFileSync(url: NSURL, completion:(path:String, error:NSError!) -> Void) {
        let documentsUrl =  NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first as! NSURL
        let destinationUrl = documentsUrl.URLByAppendingPathComponent(url.lastPathComponent!)
        if NSFileManager().fileExistsAtPath(destinationUrl.path!) {
            println("file already exists [\(destinationUrl.path!)]")
            completion(path: destinationUrl.path!, error:nil)
        } else if let dataFromURL = NSData(contentsOfURL: url){
            if dataFromURL.writeToURL(destinationUrl, atomically: true) {
                println("file saved [\(destinationUrl.path!)]")
                completion(path: destinationUrl.path!, error:nil)
            } else {
                println("error saving file")
                let error = NSError(domain:"Error saving file", code:1001, userInfo:nil)
                completion(path: destinationUrl.path!, error:error)
            }
        } else {
            let error = NSError(domain:"Error downloading file", code:1002, userInfo:nil)
            completion(path: destinationUrl.path!, error:error)
        }
    }

    class func loadFileAsync(url: NSURL, completion:(path:String, error:NSError!) -> Void) {
        let documentsUrl =  NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first as! NSURL
        let destinationUrl = documentsUrl.URLByAppendingPathComponent(url.lastPathComponent!)
        if NSFileManager().fileExistsAtPath(destinationUrl.path!) {
            println("file already exists [\(destinationUrl.path!)]")
            completion(path: destinationUrl.path!, error:nil)
        } else {
            let sessionConfig = NSURLSessionConfiguration.defaultSessionConfiguration()
            let session = NSURLSession(configuration: sessionConfig, delegate: nil, delegateQueue: nil)
            let request = NSMutableURLRequest(URL: url)
            request.HTTPMethod = "GET"
            let task = session.dataTaskWithRequest(request, completionHandler: { (data: NSData!, response: NSURLResponse!, error: NSError!) -> Void in
                if (error == nil) {
                    if let response = response as? NSHTTPURLResponse {
                        println("response=\(response)")
                        if response.statusCode == 200 {
                            if data.writeToURL(destinationUrl, atomically: true) {
                                println("file saved [\(destinationUrl.path!)]")
                                completion(path: destinationUrl.path!, error:error)
                            } else {
                                println("error saving file")
                                let error = NSError(domain:"Error saving file", code:1001, userInfo:nil)
                                completion(path: destinationUrl.path!, error:error)
                            }
                        }
                    }
                }
                else {
                    println("Failure: \(error.localizedDescription)");
                    completion(path: destinationUrl.path!, error:error)
                }
            })
            task.resume()
        }
    }
}

コードで使用する方法は次のとおりです。

let url = NSURL(string: "http://www.mywebsite.com/myfile.pdf") 
HttpDownloader.loadFileAsync(url, completion:{(path:String, error:NSError!) in
                println("pdf downloaded to: \(path)")
            })

Answer 3

Devranおよびdjunodのソリューションは、アプリケーションがフォアグラウンドにある限り機能します。ダウンロード中に別のアプリケーションに切り替えると、失敗します。私のファイルサイズは約10 MBで、ダウンロードに時間がかかります。そのため、アプリがバックグラウンドになった場合でもダウンロード機能が動作する必要があります。

[機能]で[バックグラウンドモード/バックグラウンドフェッチ]をオンにしたことに注意してください。

Completionhandlerはサポートされていなかったため、ソリューションはカプセル化されません。ごめんなさい.

--Swift 2.3--

import Foundation 
class Downloader : NSObject, NSURLSessionDownloadDelegate
{
    var url : NSURL? 
    // will be used to do whatever is needed once download is complete
    var yourOwnObject : NSObject?

    init(yourOwnObject : NSObject)
    {
        self.yourOwnObject = yourOwnObject
    }

    //is called once the download is complete
    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didFinishDownloadingToURL location: NSURL)
    {
        //copy downloaded data to your documents directory with same names as source file
        let documentsUrl =  NSFileManager.defaultManager().URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask).first
        let destinationUrl = documentsUrl!.URLByAppendingPathComponent(url!.lastPathComponent!)
        let dataFromURL = NSData(contentsOfURL: location)
        dataFromURL?.writeToURL(destinationUrl, atomically: true)

        //now it is time to do what is needed to be done after the download
        yourOwnObject!.callWhatIsNeeded()
    }

    //this is to track progress
    func URLSession(session: NSURLSession, downloadTask: NSURLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64)
    {
    }

    // if there is an error during download this will be called
    func URLSession(session: NSURLSession, task: NSURLSessionTask, didCompleteWithError error: NSError?)
    {
        if(error != nil)
        {
            //handle the error
            print("Download completed with error: \(error!.localizedDescription)");
        }
    }

    //method to be called to download
    func download(url: NSURL)
    {
        self.url = url

        //download identifier can be customized. I used the "ulr.absoluteString"
        let sessionConfig = NSURLSessionConfiguration.backgroundSessionConfigurationWithIdentifier(url.absoluteString)
        let session = NSURLSession(configuration: sessionConfig, delegate: self, delegateQueue: nil)
        let task = session.downloadTaskWithURL(url)
        task.resume()
    }
}

そして、ここに--Swift 2.3--を呼び出す方法があります

    let url = NSURL(string: "http://company.com/file.txt")
    Downloader(yourOwnObject).download(url!)

-スウィフト3--

class Downloader : NSObject, URLSessionDownloadDelegate {

var url : URL?
// will be used to do whatever is needed once download is complete
var yourOwnObject : NSObject?

init(_ yourOwnObject : NSObject)
{
    self.yourOwnObject = yourOwnObject
}

//is called once the download is complete
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL)
{
    //copy downloaded data to your documents directory with same names as source file
    let documentsUrl =  FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first
    let destinationUrl = documentsUrl!.appendingPathComponent(url!.lastPathComponent)
    let dataFromURL = NSData(contentsOf: location)
    dataFromURL?.write(to: destinationUrl, atomically: true)

    //now it is time to do what is needed to be done after the download
    yourOwnObject!.callWhatIsNeeded()
}

//this is to track progress
private func URLSession(session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64)
{
}

// if there is an error during download this will be called
func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?)
{
    if(error != nil)
    {
        //handle the error
        print("Download completed with error: \(error!.localizedDescription)");
    }
}

//method to be called to download
func download(url: URL)
{
    self.url = url

    //download identifier can be customized. I used the "ulr.absoluteString"
    let sessionConfig = URLSessionConfiguration.background(withIdentifier: url.absoluteString)
    let session = Foundation.URLSession(configuration: sessionConfig, delegate: self, delegateQueue: nil)
    let task = session.downloadTask(with: url)
    task.resume()
}}

そして、ここで呼び出す方法です--Swift 3--

    let url = URL(string: "http://company.com/file.txt")
    Downloader(yourOwnObject).download(url!)

Answer 4

テキストファイルのみをStringにダウンロードする必要がある場合は、この単純な方法を使用できます。Swift 5：

let list = try? String(contentsOf: URL(string: "https://example.com/file.txt")!)

オプションではない結果またはエラー処理が必要な場合：

do {
    let list = try String(contentsOf: URL(string: "https://example.com/file.txt")!)
}
catch {
    // Handle error here
}

ネットワーク操作がメインスレッドで実行され、UIがロックされるのを防ぐために、ネットワーク操作に時間がかかる場合があることを知っておく必要があります。たとえば、次のようにコードを非同期に実行できます。

DispatchQueue.global().async {
    let list = try? String(contentsOf: URL(string: "https://example.com/file.txt")!)
}

Answer 5

Swift 4バージョンは次のとおりです。

static func loadFileAsync(url: URL, completion: @escaping (String?, Error?) -> Void)
{
    let documentsUrl =  FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!

    let destinationUrl = documentsUrl.appendingPathComponent(url.lastPathComponent)

    if FileManager().fileExists(atPath: destinationUrl.path)
    {
        completion(destinationUrl.path, nil)
    }
    else
    {
        let session = URLSession(configuration: URLSessionConfiguration.default, delegate: nil, delegateQueue: nil)
        var request = URLRequest(url: url)
        request.httpMethod = "GET"
        let task = session.dataTask(with: request, completionHandler:
        {
            data, response, error in
            if error == nil
            {
                if let response = response as? HTTPURLResponse
                {
                    if response.statusCode == 200
                    {
                        if let data = data
                        {
                            if let _ = try? data.write(to: destinationUrl, options: Data.WritingOptions.atomic)
                            {
                                completion(destinationUrl.path, error)
                            }
                            else
                            {
                                completion(destinationUrl.path, error)
                            }
                        }
                        else
                        {
                            completion(destinationUrl.path, error)
                        }
                    }
                }
            }
            else
            {
                completion(destinationUrl.path, error)
            }
        })
        task.resume()
    }
}

Answer 6

スイフト3

あなたはこのコードを試してみたいので、一口ずつファイルをダウンロードして進行状況ビューを表示したい

import UIKit

class ViewController: UIViewController,URLSessionDownloadDelegate,UIDocumentInteractionControllerDelegate {

    @IBOutlet weak var img: UIImageView!
    @IBOutlet weak var btndown: UIButton!
    var urlLink: URL!
    var defaultSession: URLSession!
    var downloadTask: URLSessionDownloadTask!
    //var backgroundSession: URLSession!
    @IBOutlet weak var progress: UIProgressView!
    override func viewDidLoad() {
        super.viewDidLoad()

        // Do any additional setup after loading the view, typically from a nib.

        let backgroundSessionConfiguration = URLSessionConfiguration.background(withIdentifier: "backgroundSession")
        defaultSession = Foundation.URLSession(configuration: backgroundSessionConfiguration, delegate: self, delegateQueue: OperationQueue.main)
        progress.setProgress(0.0, animated: false)
    }

    func startDownloading () {
        let url = URL(string: "http://publications.gbdirect.co.uk/c_book/thecbook.pdf")!
        downloadTask = defaultSession.downloadTask(with: url)
        downloadTask.resume()
    }

    @IBAction func btndown(_ sender: UIButton) {

        startDownloading()

    }

    func showFileWithPath(path: String){
        let isFileFound:Bool? = FileManager.default.fileExists(atPath: path)
        if isFileFound == true{
            let viewer = UIDocumentInteractionController(url: URL(fileURLWithPath: path))
            viewer.delegate = self
            viewer.presentPreview(animated: true)
        }

    }


    // MARK:- URLSessionDownloadDelegate
    func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {

        print(downloadTask)
        print("File download succesfully")

        let path = NSSearchPathForDirectoriesInDomains(FileManager.SearchPathDirectory.documentDirectory, FileManager.SearchPathDomainMask.userDomainMask, true)
        let documentDirectoryPath:String = path[0]
        let fileManager = FileManager()
        let destinationURLForFile = URL(fileURLWithPath: documentDirectoryPath.appendingFormat("/file.pdf"))

        if fileManager.fileExists(atPath: destinationURLForFile.path){
            showFileWithPath(path: destinationURLForFile.path)
            print(destinationURLForFile.path)
        }
        else{
            do {
                try fileManager.moveItem(at: location, to: destinationURLForFile)
                // show file
                showFileWithPath(path: destinationURLForFile.path)
            }catch{
                print("An error occurred while moving file to destination url")
            }
        }



    }

    func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
        progress.setProgress(Float(totalBytesWritten)/Float(totalBytesExpectedToWrite), animated: true)
    }

    func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
        downloadTask = nil
        progress.setProgress(0.0, animated: true)
        if (error != nil) {
            print("didCompleteWithError \(error?.localizedDescription ?? "no value")")
        }
        else {
            print("The task finished successfully")
        }
    }

    func documentInteractionControllerViewControllerForPreview(_ controller: UIDocumentInteractionController) -> UIViewController
    {
        return self
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }


}

このコードを使用して、アプリケーションのドキュメントディレクトリにファイルストアを自動的にダウンロードする

このコードは100％動作しています

Answer 7

はい、このコードを使用してリモートURLからファイルを非常に簡単にダウンロードできます。このコードは私のためにうまく機能しています。

func DownlondFromUrl(){
   // Create destination URL 
let documentsUrl:URL =  FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first as URL!
let destinationFileUrl = documentsUrl.appendingPathComponent("downloadedFile.jpg")

//Create URL to the source file you want to download
let fileURL = URL(string: "https://s3.amazonaws.com/learn-Swift/IMG_0001.JPG")

let sessionConfig = URLSessionConfiguration.default
let session = URLSession(configuration: sessionConfig)

let request = URLRequest(url:fileURL!)

let task = session.downloadTask(with: request) { (tempLocalUrl, response, error) in
    if let tempLocalUrl = tempLocalUrl, error == nil {
        // Success
        if let statusCode = (response as? HTTPURLResponse)?.statusCode {
            print("Successfully downloaded. Status code: \(statusCode)")
        }

        do {
            try FileManager.default.copyItem(at: tempLocalUrl, to: destinationFileUrl)
        } catch (let writeError) {
            print("Error creating a file \(destinationFileUrl) : \(writeError)")
        }

    } else {
        print("Error took place while downloading a file. Error description: %@", error?.localizedDescription);
    }
}
task.resume()
}

Answer 8

このコードのみを試すSwift 3.0最初にNSオブジェクトファイルを作成作成したファイルにこのコードをコピー

import UIKit

class Downloader : NSObject, URLSessionDownloadDelegate {

    var url : URL?
    // will be used to do whatever is needed once download is complete
    var obj1 : NSObject?

    init(_ obj1 : NSObject)
    {
        self.obj1 = obj1
    }

    //is called once the download is complete
    func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL)
    {
        //copy downloaded data to your documents directory with same names as source file
        let documentsUrl =  FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first
        let destinationUrl = documentsUrl!.appendingPathComponent(url!.lastPathComponent)
        let dataFromURL = NSData(contentsOf: location)
        dataFromURL?.write(to: destinationUrl, atomically: true)

        //now it is time to do what is needed to be done after the download
        //obj1!.callWhatIsNeeded()
    }

    //this is to track progress
    private func URLSession(session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64)
    {
    }

    // if there is an error during download this will be called
    func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?)
    {
        if(error != nil)
        {
            //handle the error
            print("Download completed with error: \(error!.localizedDescription)");
        }
    }

    //method to be called to download
    func download(url: URL)
    {
        self.url = url

        //download identifier can be customized. I used the "ulr.absoluteString"
        let sessionConfig = URLSessionConfiguration.background(withIdentifier: url.absoluteString)
        let session = Foundation.URLSession(configuration: sessionConfig, delegate: self, delegateQueue: nil)
        let task = session.downloadTask(with: url)
        task.resume()
    }}

次にコードをコピーして、ファイルをダウンロードする場所にコードを配置します

 object = "http://www.mywebsite.com/myfile.pdf"
       let url1 = URL(string: object!)
        Downloader(url1! as NSObject).download(url: url1!)

Answer 9

Swift 4誰でもこれが必要な場合のバージョン

import Foundation

class FileDownloader {

    static func loadFileSync(url: URL, completion: @escaping (String?, Error?) -> Void)
    {
        let documentsUrl = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!

        let destinationUrl = documentsUrl.appendingPathComponent(url.lastPathComponent)

        if FileManager().fileExists(atPath: destinationUrl.path)
        {
            print("File already exists [\(destinationUrl.path)]")
            completion(destinationUrl.path, nil)
        }
        else if let dataFromURL = NSData(contentsOf: url)
        {
            if dataFromURL.write(to: destinationUrl, atomically: true)
            {
                print("file saved [\(destinationUrl.path)]")
                completion(destinationUrl.path, nil)
            }
            else
            {
                print("error saving file")
                let error = NSError(domain:"Error saving file", code:1001, userInfo:nil)
                completion(destinationUrl.path, error)
            }
        }
        else
        {
            let error = NSError(domain:"Error downloading file", code:1002, userInfo:nil)
            completion(destinationUrl.path, error)
        }
    }

    static func loadFileAsync(url: URL, completion: @escaping (String?, Error?) -> Void)
    {
        let documentsUrl =  FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!

        let destinationUrl = documentsUrl.appendingPathComponent(url.lastPathComponent)

        if FileManager().fileExists(atPath: destinationUrl.path)
        {
            print("File already exists [\(destinationUrl.path)]")
            completion(destinationUrl.path, nil)
        }
        else
        {
            let session = URLSession(configuration: URLSessionConfiguration.default, delegate: nil, delegateQueue: nil)
            var request = URLRequest(url: url)
            request.httpMethod = "GET"
            let task = session.dataTask(with: request, completionHandler:
            {
                data, response, error in
                if error == nil
                {
                    if let response = response as? HTTPURLResponse
                    {
                        if response.statusCode == 200
                        {
                            if let data = data
                            {
                                if let _ = try? data.write(to: destinationUrl, options: Data.WritingOptions.atomic)
                                {
                                    completion(destinationUrl.path, error)
                                }
                                else
                                {
                                    completion(destinationUrl.path, error)
                                }
                            }
                            else
                            {
                                completion(destinationUrl.path, error)
                            }
                        }
                    }
                }
                else
                {
                    completion(destinationUrl.path, error)
                }
            })
            task.resume()
        }
    }
}

このメソッドを呼び出す方法は次のとおりです。

let url = URL(string: "http://www.filedownloader.com/mydemofile.pdf")
FileDownloader.loadFileAsync(url: url!) { (path, error) in
    print("PDF File downloaded to : \(path!)")
}

Answer 10

Just のように、生活を楽にするサードパーティのライブラリを使用することもできます

Just.get("http://www.mywebsite.com/myfile.pdf")

もっと素晴らしいSwiftものがここにあります https://github.com/matteocrippa/awesome-Swift

Answer 11

スイフト3

class ViewController: UIViewController {
    var urlLink: URL!
    var defaultSession: URLSession!
    var downloadTask: URLSessionDownloadTask!
}

// MARK: Button Pressed
    @IBAction func btnDownloadPressed(_ sender: UIButton) {
        let urlLink1 = URL.init(string: "https://github.com/VivekVithlani/QRCodeReader/archive/master.Zip")
        startDownloading(url: urlLink!)
}
    @IBAction func btnResumePressed(_ sender: UIButton) {
    downloadTask.resume()
}

@IBAction func btnStopPressed(_ sender: UIButton) {
    downloadTask.cancel()
}

@IBAction func btnPausePressed(_ sender: UIButton) {
    downloadTask.suspend()
}

    func startDownloading (url:URL) {
        let backgroundSessionConfiguration = URLSessionConfiguration.background(withIdentifier: "backgroundSession")
        defaultSession = Foundation.URLSession(configuration: backgroundSessionConfiguration, delegate: self, delegateQueue: OperationQueue.main)
        downloadProgress.setProgress(0.0, animated: false)
        downloadTask = defaultSession.downloadTask(with: urlLink)
        downloadTask.resume()
    }

// MARK:- URLSessionDownloadDelegate
func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didFinishDownloadingTo location: URL) {
    print("File download succesfully")
}

func urlSession(_ session: URLSession, downloadTask: URLSessionDownloadTask, didWriteData bytesWritten: Int64, totalBytesWritten: Int64, totalBytesExpectedToWrite: Int64) {
    downloadProgress.setProgress(Float(totalBytesWritten)/Float(totalBytesExpectedToWrite), animated: true)
}

func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?) {
    downloadTask = nil
    downloadProgress.setProgress(0.0, animated: true)
    if (error != nil) {
        print("didCompleteWithError \(error?.localizedDescription)")
    }
    else {
        print("The task finished successfully")
    }
}