Play/Forward video in 2x 3x 4x speed in mobilevlck

Question

In my project, I code trickplay like the following, but the code didn't work.How to solve this problem. If you guys have any ideas, help me .

func didTrickPlayValueChanged(_ atRate: Float!){
            if( atRate == 1.0){

                vlcMediaPlayer.fastForward(atRate: 1.00)
            }
            else if(atRate == 2.0){

                vlcMediaPlayer.fastForward(atRate: 2.00)

            }
            else if(atRate == -2.0){

                vlcMediaPlayer.fastForward(atRate: -2.00)

            }
            else if(atRate == -1.0){

                vlcMediaPlayer.fastForward(atRate: -1.00)
            }else{
                vlcMediaPlayer.fastForward(atRate: 1.00)
            }
        }