Express 中间件错误

Question

我正在制作一个 API 接受视频并将其上传到 cloudinary。然后将有关上传的元数据返回给用户。当我尝试在中间件中处理视频时，出现了我遇到的问题。我不确定为什么我一直收到此错误。

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)

下面的项目代码：

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;

uploadtocloudinary.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;

generatevideothumbnail.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，对于随所需文件发送的内容有几种不同的选择。您可以发送整个对象，也可以发送特定函数。

使用 module.exports.uploadToCloudinary= 和 module.exports.generateThumbnail=，您将发送一个包含函数 uploadToCloudinary 和 generateThumbnail 的对象。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，要访问你想要的功能，你必须写：

 createThumbnail.generateThumbnail

如果你只想在引入所需文件时只能使用一个特定的函数，只需将函数的名称给module.exports，就像这样：

module.exports = generateVideoThumbnail;

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

让我知道这是否有意义。

Express 中间件错误

Express middleware error

javascript

middleware

express