Small UIImageView extension and download helper to quickly set a user picture from www.uifaces.com on a UIImageView

UIFaces.swift

import UIKit

typealias JSON = [String: AnyObject]
public typealias ImageRequestCompletion = (UIImage?, NSError?) -> Void

public enum UserImageSize: String {
    case Epic = "epic"
    case Big = "bigger"
    case Normal = "normal"
    case Tiny = "mini"
}

public class ImageDownloader: NSObject {

    private static let uiFacesURL = NSURL(string: "http://uifaces.com/api/v1/random")!

    public class func getUserImage(size: UserImageSize = .Normal, completion: ImageRequestCompletion) {
        let task = NSURLSession.sharedSession().dataTaskWithURL(uiFacesURL) { data, _, error in
            if error != nil {
                completion(nil, error)
            }
            var jsonError: NSError? = nil
            let json = NSJSONSerialization.JSONObjectWithData(data, options: .MutableLeaves, error: &jsonError) as? JSON
            if jsonError != nil {
                completion(nil, jsonError)
            }
            if let json = json, paths = json["image_urls"] as? JSON, path = paths[size.rawValue] as? String, url = NSURL(string: path) {
                self.getImage(url, completion: completion)
            } else {
                completion(nil, NSError(domain: "Error parsing JSON data", code: 0, userInfo: nil))
            }
        }
        task.resume()
    }

    private class func getImage(url: NSURL, completion: ImageRequestCompletion) {
            let task = NSURLSession.sharedSession().dataTaskWithURL(url) { data, _, error in
                if let data = data, image = UIImage(data: data) {
                    completion(image, nil)
                } else {
                    completion(nil, error)
                }
            }
            task.resume()
        }
}

public extension UIImageView {
    convenience init(size: UserImageSize) {
        self.init()
        loadUserImage(size)
    }

    func loadUserImage(size: UserImageSize) {
        ImageDownloader.getUserImage(size: size) { image, error in
            if error != nil {
                println("Error getting image: \(error)")
            } else {
                dispatch_async(dispatch_get_main_queue()) {
                    self.image = image
                }
            }
        }
    }
}