Get mime type using MobileCoreServices framework

MimeType.swift

import MobileCoreServices

fileprivate let defaultMimeType = "application/octet-stream"

protocol PathExtensionable {
  var pathExtension: String? { get }
}

extension URL : PathExtensionable {
  var pathExtension: String? {
    return NSURL(fileURLWithPath: self.path).pathExtension
  }
}

extension String : PathExtensionable {
  var pathExtension: String? {
    return URL(string: self)?.pathExtension
  }
}

extension PathExtensionable {
  func mimeType() -> String {
    guard let pathExt = pathExtension else {
      return defaultMimeType
    }
    
    if let uti = UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension, pathExt as CFString, nil)?.takeRetainedValue() {
      if let mimeType = UTTypeCopyPreferredTagWithClass(uti, kUTTagClassMIMEType)?.takeRetainedValue() {
        return mimeType as String
      }
    }
    
    return defaultMimeType
  }
}