javascript - Express中间件错误

Question

我正在制作一个 API，它接受视频并将其上传到 cloudinary。然后，有关上传的元数据将返回给用户。当我尝试在中间件中处理视频时，出现了我遇到的问题。我不知道为什么我总是收到此错误。

错误:

/Users/name/test/cloudinary_upload/node_modules/express/lib/router/route.js:196
        throw new Error(msg);
        ^

Error: Route.post() requires callback functions but got a [object Object]
    at Route.(anonymous function) [as post] (/Users/name/test/cloudinary_upload/node_modules/express/lib/router/route.js:196:15)
    at Function.proto.(anonymous function) [as post] (/Users/name/test/cloudinary_upload/node_modules/express/lib/router/index.js:510:19)
    at Object.<anonymous> (/Users/name/test/cloudinary_upload/routes.js:8:8)
    at Module._compile (module.js:541:32)
    at Object.Module._extensions..js (module.js:550:10)
    at Module.load (module.js:458:32)
    at tryModuleLoad (module.js:417:12)
    at Function.Module._load (module.js:409:3)
    at Module.require (module.js:468:17)
    at require (internal/module.js:20:19)

项目代码如下:

app.js

'use strict';

var express = require('express');
var formidable = require('express-formidable');
var port = process.env.PORT || 3000;
var routes = require('./routes');
var app = express();

// Parse incoming request
app.use(formidable());

app.use('/routes', routes);

// Catch 404 and forward to error handler
app.use(function(req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

// Error handler
app.use(function(err, req, res, next) {
  res.status(err.status || 500);
  res.json({
    error: {
      message: err.message
    }
  });
});


app.listen(port, function() {
  console.log('Express server is listening on port ' + port);
});

routes.js

'use strict';

var express = require('express');
var createThumbnail = require('./middleware/generatevideothumbnail');
var uploadToCloudinary = require('./middleware/uploadtocloudinary');
var router = express.Router();

router.post('/upload', uploadToCloudinary, createThumbnail, function(req, res, next) {
  console.log(req.cloudinaryObject);
  console.log(req.videoThumbnail);
  res.json(req.cloudinaryObject);
});

module.exports = router;

上传到cloudinary.js

'use strict';

var cloudinary = require('../cloudinary_config.js').cloudinary;

/************************************************************
MIDDLEWARE: Accepts the request object. Uploads the video
file to cloudinary. Passes the video's public id, version, file
type, time of upload, file size and url to the next middleware
on the request object.
 ************************************************************/
function uploadToCloudinary(req, res, next) {
  cloudinary.uploader.upload(req.files.fileToUpload.path, function(resultOfUpload) {
    var cloudinaryObject = {
       public_id: resultOfUpload.public_id,
       version: resultOfUpload.version,
       typeOfFile: resultOfUpload.format, // Type of file
       uploadTime: resultOfUpload.created_at, // Upload time
       fileSize: resultOfUpload.bytes, // File size
       videoUrl: resultOfUpload.secure_url // Video URL
     }

    req.cloudinaryObject = cloudinaryObject;

    next();
  }, {
    resource_type: "video"
  });
}

module.exports.uploadToCloudinary = uploadToCloudinary;

生成视频缩略图.js

'use strict';

/************************************************************
MIDDLEWARE: Accepts the request object. Use the version and
public id of video to create thumbnail url string. Pass
thumbnail url to next middleware on the request object.
 ************************************************************/
 function generateVideoThumbnail(req, res, next) {
  req.videoThumbnail = "https://res.cloudinary.com/xxxxxxxxx/video/upload/v"
                       + req.cloudinaryObject.version
                       + "/"
                       + req.cloudinaryObject.public_id
                       + ".jpg";

  next()
}

module.exports.generateThumbnail = generateVideoThumbnail;

Answer 1

当您使用module.exports时，对于与所需文件一起发送的内容有几种不同的选择。您可以发送整个对象，也可以发送特定的函数。

使用 module.exports.uploadToCloudinary= 和 module.exports.generateThumbnail=，您将发送一个包含函数 uploadToCloudinary 和生成缩略图。当您需要它时，例​​如，

var createThumbnail = require('./middleware/generatevideothumbnail'); 

您可以在要导出的对象上使用函数generateThumbnail。换句话说，要访问您想要的功能，您必须编写:

 createThumbnail.generateThumbnail

如果您只想在引入所需文件时仅使用一个特定函数，只需将该函数的名称赋予 module.exports，如下所示:

module.exports = generateVideoThumbnail;

引用: https://www.sitepoint.com/understanding-module-exports-exports-node-js/和 https://nodejs.org/api/modules.html

请告诉我这是否有意义。