UIImageView set image with url

UIImageView+setImageWithURL.swift

extension UIImageView {
    func setImageWithUrlString(str: String?) {
        if let url = NSURL(string: str ?? "") {
            setImageWithURL(url)
        }
    }
    
    func setImageWithURL(url: NSURL) {
        NSURLSession.sharedSession().dataTaskWithURL(url) { (data, response, error) -> Void in
            dispatch_async(dispatch_get_main_queue()) { () -> Void in
                guard data != nil else { return }
                self.image = UIImage(data: data!)
            }
        }.resume()
    }
}