Subclassing CIFilter in Swift

I am trying to create a subclass CIFilter

like this:

class ColorMonochromeFilter: CIFilter {

    required init(red: CGFloat!, green: CGFloat!, blue: CGFloat!) {

        super.init(name: "ColorMonochrome")
        setDefaults()

        let colour = UIColor(red: red, green: green, blue: blue, alpha: 1.0)
        setValue(colour, forKey: kCIInputColorKey)
    }
}

      

        
        
        
      

    

The following error messages appear:

• Class 'ColorMonochromeFilter' does not implement its superclass required members
• Must call the designated initializer superclass 'CIFilter'

It seems that the designated initializer is init(coder aDecoder: NSCoder!)

due to CIFilter

conforming to the protocol NSCoding

rather than the init(name: String!)

one declared in the extension on CIFilter

.

I can remove the first error by adding:

    required init(coder aDecoder: NSCoder!) {
        super.init(coder: aDecoder)
    }

      

        
        
        
      

    

(although it seems a little overkill!)

Is there a way to solve the second problem?

What I am trying to achieve is the Swift equivalent:

@implementation ASHColorMonochromeFilter

    + (ASHColorMonochromeFilter *) filterWithRed: (CGFloat) red green:(CGFloat)green blue:(CGFloat)blue
    {
        ASHColorMonochromeFilter * filter = (ASHColorMonochromeFilter *)[ASHColorMonochromeFilter filterWithName: @"CIColorMonochrome"];

        UIColor * color = [UIColor colorWithRed: red green: green blue: blue alpha: 1.0];
        [filter setValue: color forKey: kCIImageColorSpace];

        return filter;
    }