title: Download music file from server and save in my app
body: <p>I need to download an .mp3 audio file from a server to save in my app and play it without downloading, exactly like the screenshot below, with a progress  bar for the download (I found this in the App Store). Can anyone help me to do this in my app, with source code?
  Any help will be appreciated! Thanks in advance!</p>
  
  <p>I used <code>NSURLConnection</code> but it does not really work for me.</p>
  
  <p>Here is the screenshot of what I am trying to do.</p>
  
  <p><img src="https://i.stack.imgur.com/W8iM2.png" alt="Screenshot of download with progress bar"></p>