无法转换“nsStoryboardSegue.identifier”类型的值?到所需的参数类型“string”

im使用以下代码显示视图控制器,im使用identifier属性标识segue。

无法转换'nsStoryboardSegue.Identifier'类型的值。到所需的参数类型“string”

override func prepare(for segue: NSStoryboardSegue, sender: Any?) {
    if (segue.identifier == "segue") {
        //get a reference to the destination view controller
        let destinationVC:ProgressView = segue.destinationController as! ProgressView

        //set properties on the destination view controller
        destinationVC.fileArray=fileArray
        destinationVC.croptype=croptype
        destinationVC.outdir=outdir
        destinationVC.fileformat=fileformat
        destinationVC.tflag=tflag
        if(resize==true)
        {
        destinationVC.resize=true
        destinationVC.rwidth=rwidth
        destinationVC.rheight=rheight
        destinationVC.preserve_aspect_ratio=preserve_aspect_ratio
        }

    }
}

请给我建议