playShufflePressed.swift

// 隨機播放，預設無，點選變成有
    @IBAction func playShufflePressed(_ sender: UIButton) {
        switch shuffleType {
        case .no:
            shuffleType = .yes
            playShuffle.setImage(UIImage(systemName: SystemName.shuffleCircleFill), for: .normal)
            songs?.shuffle()
        case .yes:
            shuffleType = .no
            playShuffle.setImage(UIImage(systemName: SystemName.shuffleCircle), for: .normal)
            // 將歌單改回預設
            songs = songDefault
        }
    }