Nodejs入门遇到的问题，formidable上传图片时报错

基本上是根据Nodejs入门一步步做的，代码也基本一样： index.js:

var server = require('./server.js');
var router = require('./router.js');
var requestHandlers = require('./requestHandlers.js');

var handle = {};
handle['/'] = requestHandlers.start;
handle['/start'] = requestHandlers.start;
handle['/upload'] = requestHandlers.upload;
handle['/show'] = requestHandlers.show;

server.start(router.route,handle);

server.js:

var http = require("http");
var url = require('url');
exports.start = function(route, handle){
    http.createServer(function(request, response){
        var pathname = url.parse(request.url).pathname;
        route(handle, pathname, response, request);
    }).listen(3000);
    console.log('Server has started!');
};

router.js:

function route (handle, pathname, response, request) {
    console.log('A request for' + pathname);

    if(typeof handle[pathname] === 'function'){
        handle[pathname](response, request);
    }else{
        console.log('No request handler for ' + pathname);

        response.writeHead(404, {'Content-Type': 'text/plain'});
        response.write('404 not found');
        response.end();
    }
}
exports.route = route;

requestHandler.js:

var querystring = require('querystring'),
    fs = require('fs'),
    formidable = require('formidable'),
    util = require('util');

function start (response) {
    console.log('Request handler "start" was called.');

    var body = '<html>'+
                '<head>'+
                '<meta http-equiv="Content-Type" content="text/html; '+
                'charset=UTF-8" />'+
                '</head>'+
                '<body>'+
                '<form action="/upload" method="post" enctype="multipart/form-data">'+
                '<input type="file" name="upload" multiple="multiple">'+
                '<input type="submit" value="Upload file" />'+
                '</form>'+
                '</body>'+
                '</html>';
    response.writeHead(200, {'Content-Type': 'text/html'});
    response.write(body);
    response.end();
}
function upload (response, request) {
    console.log('Request handler "upload" was called.');

    var form = new formidable.IncomingForm();
    form.uploadDir = 'tmp';
    form.parse(request, function(error, fields, files){
        //fs.renameSync(files.upload.path, '/tmp/test.png');
        try{
            console.log(files.upload.path);
        }catch(e){
            console.log(e);
        }
        response.writeHead(200, {'Content-Type': 'text/html'});
        response.write('Received image: <br>');
        response.write('<img src="/show" />');
        response.end();
    });
    
}
function show (response) {
    console.log('Request handler "show" was called.');
    fs.readFile('/tmp/test.png', 'binary', function(error, file) {
        if(error){
            response.writeHead(500, {'Content-Type': 'text/plain'});
            response.write(error + '\n');
            response.end();
        }else{
            response.writeHead(200, {'Content-Type': 'image/png'});
            response.write(file, 'binary');
            response.end();
        }
    });
}
exports.start = start;
exports.upload = upload;
exports.show = show;

###报错信息： Cannot read property ‘path’ of undefined

####打印files的结果：

{ upload:
   { domain: null,
     _events: {},
     _maxListeners: 10,
     size: 2722,
     path: 'tmp\\2d3ead58151f69465f4fec03b2e27b34',
     name: 'image-holder.png',
     type: 'image/png',
     hash: null,
     lastModifiedDate: Tue May 06 2014 16:44:50 GMT+0800 (中国标准时间),
     _writeStream:
      { _writableState: [Object],
        writable: true,
        domain: null,
        _events: {},
        _maxListeners: 10,
        path: 'tmp\\2d3ead58151f69465f4fec03b2e27b34',
        fd: null,
        flags: 'w',
        mode: 438,
        start: undefined,
        pos: undefined,
        bytesWritten: 2722,
        closed: true } } }

之前看到有人提过这个问题链接，是因为自己设置了encoding，但是我没设置也是这个问题，各位大神帮忙看一下到底哪里有问题啊