无法转换类型'的值（AFMultipartFormData！） - ＆gt; Void'到预期的参数类型'（（AFMultipartFormData？） - ＆gt; Void）！'

Question

我正在尝试使用AFNetworking＆amp; swift 3.0，但我收到如下错误。 Cannot convert value of type '(AFMultipartFormData!) -> Void' to expected argument type '((AFMultipartFormData?) -> Void)!'

    let url = "http://localhost:9000/api/content"

    var params = [
        "familyId":"10000",
        "contentBody" : "Some body content for the test application",
        "name" : "the name/title",
        "typeOfContent":"photo"
    ]

    let manager = AFHTTPRequestOperationManager()
    manager.post(
        url,
        parameters: params,
        constructingBodyWith: { (formData: AFMultipartFormData!) -> Void in
            formData.appendPartWithFileData(imageData!, name: "Photo", fileName: "photo.jpg", mimeType: "image/jpeg")
    },
        success: { (operation: AFHTTPRequestOperation?, responseObject: Any?) in

            self.onSuccess(
                operation: operation!,
                responseObject: responseObject! as AnyObject
            )
    },
        failure: { (operation: AFHTTPRequestOperation?, error) in
            print("Error 1: " + error!.localizedDescription)

            self.onFailure(operation: operation)
    })

有人知道如何解决这个问题吗？ 任何帮助将不胜感激。提前谢谢。