Send emails with attachments in iOS using Swift

ViewController.swift

//
//  ViewController.swift
//  SendEmailWithAttachment
//
//  Created by Kelly Egan on 3/17/15.
//  Copyright (c) 2015 Kelly Egan. All rights reserved.
//

import UIKit
import MessageUI

class ViewController: UIViewController, MFMailComposeViewControllerDelegate {

    @IBOutlet weak var emailButton: UIButton!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
    }

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

    @IBAction func sendEmail(sender: UIButton) {
        //Check to see the device can send email.
        if( MFMailComposeViewController.canSendMail() ) {
            println("Can send email.")
            
            let mailComposer = MFMailComposeViewController()
            mailComposer.mailComposeDelegate = self

            //Set the subject and message of the email
            mailComposer.setSubject("Have you heard a swift?")
            mailComposer.setMessageBody("This is what they sound like.", isHTML: false)

            if let filePath = NSBundle.mainBundle().pathForResource("swifts", ofType: "wav") {
                println("File path loaded.")
                
                if let fileData = NSData(contentsOfFile: filePath) {
                    println("File data loaded.")
                    mailComposer.addAttachmentData(fileData, mimeType: "audio/wav", fileName: "swifts")
                }
            }
            self.presentViewController(mailComposer, animated: true, completion: nil)
        }
    }
    
    func mailComposeController(controller: MFMailComposeViewController!, didFinishWithResult result: MFMailComposeResult, error: NSError!) {
        self.dismissViewControllerAnimated(true, completion: nil)
    }
}

I want to download through URL from backend side so i don't know file type so what is the value are passed, And yes URL param like images, pdf, mp3 any type of file.

find out ContentMIMEType here https://gist.github.com/AshvinGudaliya/6f9cfb2e7c90453161cfc3adfa758819