CFDictionary and Swift 2.1

gistfile1.txt

    //In Swift 1.x this works and `properties` are casted to `[NSObject: AnyObject]`:
    
    func imageOwnerWithURL(url: NSURL) -> ZMImageOwner! {
        if let source = CGImageSourceCreateWithURL(url, nil),
            properties = CGImageSourceCopyPropertiesAtIndex(source, 0, nil) as? [NSObject: AnyObject],
            imageWidth = (properties[kCGImagePropertyPixelWidth] as? NSNumber)?.floatValue,
            imageHeight = (properties[kCGImagePropertyPixelHeight] as? NSNumber)?.floatValue,
            data = NSData(contentsOfURL: url) where acceptableSourceType(source) {
            return ImageOwner(data: data, size: CGSizeMake(CGFloat(imageWidth), CGFloat(imageHeight)), nonce: self.nonce)
        }
        return nil
    }
    
    //In Swift 2 as? [NSObject: AnyObject], but this works:
    
    func imageOwnerWithURL(url: NSURL) -> ZMImageOwner! {
      if let source = CGImageSourceCreateWithURL(url, nil),
          properties = CGImageSourceCopyPropertiesAtIndex(source, 0, nil) as Dictionary?,
          imageWidth = (properties[kCGImagePropertyPixelWidth] as? NSNumber)?.floatValue,
          imageHeight = (properties[kCGImagePropertyPixelHeight] as? NSNumber)?.floatValue,
          data = NSData(contentsOfURL: url) where acceptableSourceType(source) {
          return ImageOwner(data: data, size: CGSizeMake(CGFloat(imageWidth), CGFloat(imageHeight)), nonce: self.nonce)
        }
        return nil
    }