Extension to load an external image

InterfaceController.swift

//
//  InterfaceController.swift
//  AsnycCall WatchKit Extension
//
//  Created by Fabian Nöthe on 05.04.15.
//  Copyright (c) 2015. All rights reserved.
//

import WatchKit

class InterfaceController: WKInterfaceController {

    @IBOutlet weak var imageView: WKInterfaceImage!

    override func awakeWithContext(context: AnyObject?) {
        super.awakeWithContext(context)
    }

    override func willActivate() {
        super.willActivate()

        let image_url:String = "http://placehold.it/350x150"
        self.imageView.setImageWithUrl(image_url)
    }

    override func didDeactivate() {
        super.didDeactivate()
    }

}

WKInterfaceImage+SetImageWithUrl.swift

//
//  WKInterfaceImage+SetImageWithUrl.swift
//  AsnycCall
//
//  Created by Fabian Nöthe on 05.04.15.
//  Copyright (c) 2015. All rights reserved.
//
import WatchKit

public extension WKInterfaceImage {
    
    public func setImageWithUrl(url:String) -> WKInterfaceImage? {
        
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) {
            let url:NSURL = NSURL(string:url)!
            var data:NSData = NSData(contentsOfURL: url)!
            var placeholder = UIImage(data: data)!
            
            dispatch_async(dispatch_get_main_queue()) {
                self.setImage(placeholder)
            }
        }
        
        return self
    }
    
}