protocol

申明协议

public protocol MTLCLInputDelegate : NSObjectProtocol {

    func renderImage(ciImage : CIImage)

}

遵守协议

extension MTLCLImage : MTLCLInputDelegate {

    func renderImage(ciImage: CIImage) {

    }

}

使用时，若是申明遵守该协议，则调用时传入非法对象，报错

 var targets = [MTLCLInputDelegate]()

 func addTarget(target : MTLCLInputDelegate) {

 }