swift3 – 解决对appendingPathComponent错误的模糊使用

以下代码在我使用 swift 2.2发布和更新的应用程序中运行良好.我只是迁移到swift 3,现在我得到以下编译时错误; “使用appendingPathComponent”与行的模糊使用：

let PDFPathFilename = documentDirectory.appendingPathComponent(filename as String)

在这：

func returnPDFPath() -> String {
      let path:NSArray =         NSSearchPathForDirectoriesInDomains(.documentDirectory,.userDomainMask,truE) as NSArray
      let documentDirectory: AnyObject = path.object(at: 0) as AnyObject
      let PDFPathFilename = documentDirectory.appendingPathComponent(filename as String)

      return PDFPathFilename
 }

 @IBACtion func reveiwPDFSendCliked(_ sender: AnyObject) {

    let pdfPathWithFilename = returnPDFPath()

    generatePDFs(pdfPathWithFileName)
 }

此代码负责将文件路径返回到documentDirectory,该文件路径将在用户单击查看并保存PDF按钮时用于保存PDF文件.任何建议将不胜感激.

let documentDirectory: AnyObject = path.object(at: 0) as AnyObject

let documentDirectory = path.object(at: 0) as! NSString

func returnPDFPath() -> String {
    let path = NSSearchPathForDirectoriesInDomains(.documentDirectory,truE)
    let documentDirectory = path.first! as NSString
    let PDFPathFilename = documentDirectory.appendingPathComponent(filename as String)

    return PDFPathFilename
}