在node.js控制器中使用Next() [英] the use of Next() in a node.js controller

问题描述

我正在关注出色的node-express-mongoose-demo应用程序(

I am following the wonderful node-express-mongoose-demo app (link

在articles.js控制器中，.load函数具有next()语句，对此我感到困惑-我认为next()仅用于路由，将流程传递给下一个中间件.为什么在控制器内部在此使用next()?以及为什么其他控制器功能(例如.edit，请参见下面的代码)未使用next()..

in the articles.js controller, the .load function has a next() statement and I am confused about it - I thought that next() was only used in routing, passing the flow to the next middleware. why is next() being used here inside a controller? and why are the other controller functions (e.g. .edit ,see code below) NOT using next()..?

 /**
 * Module dependencies.
 */

var mongoose = require('mongoose')
  , Article = mongoose.model('Article')
  , utils = require('../../lib/utils')
  , extend = require('util')._extend

/**
 * Load
 */

exports.load = function(req, res, next, id){
  var User = mongoose.model('User')

  Article.load(id, function (err, article) {
    if (err) return next(err)
    if (!article) return next(new Error('not found'))
    req.article = article
    next()
  })
}

....

/**
 * Edit an article
 */

exports.edit = function (req, res) {
  res.render('articles/edit', {
    title: 'Edit ' + req.article.title,
    article: req.article
  })
}

推荐答案

.load 中间件正在调用 next()，因为它是

The .load middleware is calling next() because it is a parameter middleware. These special middlewares allow you to perform logic for specific route parameters. This can be handy if you have a route like /users/:id where you could set up a parameter middleware for id that loads that particular user's profile from the database and then continues on to the actual route handler (which now has the user's profile already available to it). Without this, you may find yourself repeating the same loading logic inside route handlers for different HTTP verbs for the same route path.

常规路由处理程序(例如 edit )不使用 next()，因为它们不需要(除非您遇到类似HTTP 500的严重错误)并想调用 next(err)).通常，它们是将响应发送回客户端的响应.

The normal route handlers (e.g. edit) don't use next() because they don't need to (unless you encounter a serious HTTP 500-like error and want to call next(err) for example). They typically are the ones that send the response back to the client.

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