title: Path extension and MIME type of file in swift
body: <p>I'm learning swift , and I made a table with cells that show an image ,and classes in groups by MIME TYPE (using path extension).
   I had a question about extensions.
   If the images (for example, it could be a video or a pdf) are taken from internet , i'm not sure if they have the extension or not 
  <strong>how can I get the MIMEtype of a file inside my file System without using path extension ?</strong>
  PS :Sorry for my bad english it's not my native language</p>