Download file from server using Swift - swift

Question

Hi I have a whole bunch of .mp3 files I want to use with NSFileManager and store in the documents folder. Is there a way I can download the .mp3 files online and then have it save to the documents folder? This is what I'm using for a local file.
let filemanager = NSFileManager.defaultManager()
let documentsPath : AnyObject = NSSearchPathForDirectoriesInDomains(.DocumentDirectory,.UserDomainMask,true)[0]
let destinationPath:NSString = documentsPath.stringByAppendingString("/Attention.mp3")
if (!filemanager.fileExistsAtPath(destinationPath)) {
var theError: NSError?
let fileForCopy = NSBundle.mainBundle().pathForResource("Attention",ofType:"mp3")
filemanager.copyItemAtPath(fileForCopy!,toPath:destinationPath, error: &theError)
if (theError == nil) {
println("The music files has been saved.")
} else {
println("Error")
}
} else {
println("The files already exist")
}

Answer 1

edit/update: Xcode 11.5 • Swift 5.2
import UIKit
import AVFoundation
class ViewController: UIViewController {
var player: AVPlayer!
override func viewDidLoad() {
super.viewDidLoad()
let alarm = URL(string: "https://www.ringtonemobi.com/storage/upload/user_id_1/iphone-5-alarm-2016-08-21-01-49-25.mp3")!
do {
try alarm.download(to: .documentDirectory) { url, error in
guard let url = url else { return }
self.player = AVPlayer(url: url)
self.player.play()
}
} catch {
print(error)
}
}
}
import Foundation
extension URL {
func download(to directory: FileManager.SearchPathDirectory, using fileName: String? = nil, overwrite: Bool = false, completion: #escaping (URL?, Error?) -> Void) throws {
let directory = try FileManager.default.url(for: directory, in: .userDomainMask, appropriateFor: nil, create: true)
let destination: URL
if let fileName = fileName {
destination = directory
.appendingPathComponent(fileName)
.appendingPathExtension(self.pathExtension)
} else {
destination = directory
.appendingPathComponent(lastPathComponent)
}
if !overwrite, FileManager.default.fileExists(atPath: destination.path) {
completion(destination, nil)
return
}
URLSession.shared.downloadTask(with: self) { location, _, error in
guard let location = location else {
completion(nil, error)
return
}
do {
if overwrite, FileManager.default.fileExists(atPath: destination.path) {
try FileManager.default.removeItem(at: destination)
}
try FileManager.default.moveItem(at: location, to: destination)
completion(destination, nil)
} catch {
print(error)
}
}.resume()
}
}
Original answer
Xcode 8.3.2 • Swift 3.1
if let audioUrl = URL(string: "http://freetone.org/ring/stan/iPhone_5-Alarm.mp3") {
// create your document folder url
let documentsUrl = try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
// your destination file url
let destination = documentsUrl.appendingPathComponent(audioUrl.lastPathComponent)
print(destination)
// check if it exists before downloading it
if FileManager.default.fileExists(atPath: destination.path) {
print("The file already exists at path")
} else {
// if the file doesn't exist
// just download the data from your url
URLSession.shared.downloadTask(with: audioUrl, completionHandler: { (location, response, error) in
// after downloading your data you need to save it to your destination url
guard
let httpURLResponse = response as? HTTPURLResponse, httpURLResponse.statusCode == 200,
let mimeType = response?.mimeType, mimeType.hasPrefix("audio"),
let location = location, error == nil
else { return }
do {
try FileManager.default.moveItem(at: location, to: destination)
print("file saved")
} catch {
print(error)
}
}).resume()
}
}

Answer 2

Xcode 10.1, Swift 4
I used the example above from #leo-dabus but broke up the code a bit into two functions. One flaw I found in that approach was that it did not handle the case where the file is already downloaded.
This example will remove any previous file that was already downloaded and write the latest version.
/// Downloads a file asynchronously
func loadFileAsync(url: URL, completion: #escaping (Bool) -> Void) {
// create your document folder url
let documentsUrl = try! FileManager.default.url(for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: true)
// your destination file url
let destination = documentsUrl.appendingPathComponent(url.lastPathComponent)
log.info(m: "downloading file from URL: \(url.absoluteString)")
if FileManager().fileExists(atPath: destination.path) {
print("The file already exists at path, deleting and replacing with latest")
if FileManager().isDeletableFile(atPath: destination.path){
do{
try FileManager().removeItem(at: destination)
print("previous file deleted")
self.saveFile(url: url, destination: destination) { (complete) in
if complete{
completion(true)
}else{
completion(false)
}
}
}catch{
print("current file could not be deleted")
}
}
// download the data from your url
}else{
self.saveFile(url: url, destination: destination) { (complete) in
if complete{
completion(true)
}else{
completion(false)
}
}
}
}
func saveFile(url: URL, destination: URL, completion: #escaping (Bool) -> Void){
URLSession.shared.downloadTask(with: url, completionHandler: { (location, response, error) in
// after downloading your data you need to save it to your destination url
guard
let httpURLResponse = response as? HTTPURLResponse, httpURLResponse.statusCode == 200,
let location = location, error == nil
else { print("error with the url response"); completion(false); return}
do {
try FileManager.default.moveItem(at: location, to: destination)
print("new file saved")
completion(true)
} catch {
print("file could not be saved: \(error)")
completion(false)
}
}).resume()
}

Answer 3

I found the #leo-dabus worked straight away, but had to make two minor changes for my needs. This might be helpful for others.
Change #1: Handle filenames that come included with a path-extension
if let fileName = fileName {
if fileName.hasSuffix(self.pathExtension) {
destination = directory
.appendingPathComponent(fileName)
} else {
destination = directory
.appendingPathComponent(fileName)
.appendingPathExtension(self.pathExtension)
}
} else {
destination = directory
.appendingPathComponent(lastPathComponent)
}
Change #2: If the destination file exists, generate a unique name
E.g. generate File (2).txt to avoid overwriting File.txt, like a web browser would.
if !overwrite {
let pathExtension = destination.pathExtension
let lastComponent = destination.deletingPathExtension().lastPathComponent
var copyNumber = 2
var attemptedURL = destination
while FileManager.default.fileExists(atPath: attemptedURL.path) {
attemptedURL = destination
.deletingPathExtension()
.deletingLastPathComponent()
.appendingPathComponent("\(lastComponent) (\(copyNumber))")
.appendingPathExtension(pathExtension)
copyNumber += 1
}
destination = attemptedURL
}