因此，您可能会写: authorController.findAuthorsByFirstAndLastName = function(req，res，next){如果(！(req.query.firstName || req.query.lastName)){res.locals.getFullAuthorList = true返回next()} 别的 {const查询=/*不管*/Author.find(query，(err，authors)=> {如果(err)返回next(err)res.locals.authors =作者下一个()})}}authorController.author_list = function(req，res，next){如果(！res.locals.getFullAuthorList)返回next()//如果我们已经有作者，则无需执行任何操作Author.find({}，(err，authors)=> {如果(err)返回next(err)res.locals.authors =作者下一个()})} 然后在您的路线中，您会说: router.get('/'，authorController.findAuthorsByFirstAndLastName，authorController.author_list，(req，res)=> {res.json({authors:res.locals.authors})}) 如果您以前从未见过 res.locals ，则它只是响应对象上的一个属性，可用于附加内容.它会在请求/响应周期中持续存在，并为每个新请求清除.I'm trying to make a catch-all of sorts to return data to my Author endpoint. If the url that is passed to the endpoint contains no query parameters, I want the router to return the full list of authors available. If the url contains firstName and lastName parameters, I want the controller to find the authors that match and, pass that data back to the router.Currently if I send the urls http://localhost:3001/authors or http://localhost:3001/authors?firstName=tom&lastName=dooly, I get an error Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client.Can anyone tell me why this is happening and how to fix it?main:var express = require('express');var path = require('path');var favicon = require('serve-favicon');var logger = require('morgan');var cookieParser = require('cookie-parser');var bodyParser = require('body-parser');var mongoose = require('mongoose');var app = express();var dev_db_url = 'mongodb://localhost:27017/'var mongoDB = process.env.MONGODB_URI || dev_db_url;mongoose.connect(dev_db_url);mongoose.Promise = global.Promise;var db = mongoose.connection;db.on('error', console.error.bind(console, 'MongoDB connection error:'));// view engine setupapp.set('views', path.join(__dirname, 'views'));app.set('view engine', 'jade');// uncomment after placing your favicon in /public//app.use(favicon(path.join(__dirname, 'public', 'favicon.ico')));app.use(logger('dev'));app.use(bodyParser.json());app.use(bodyParser.urlencoded({ extended: false }));app.use(cookieParser());app.use(express.static(path.join(__dirname, 'public')));var index = require('./routes/index');var users = require('./routes/users');var feedEntries = require('./routes/feedEntries');var authors = require('./routes/authors');app.use('/', index);app.use('/users', users);app.use('/feedEntries', feedEntries);app.use('/authors', authors);// catch 404 and forward to error handlerapp.use(function(req, res, next) { var err = new Error('Not not Found'); err.status = 404; next(err);});app.use(function(err, req, res, next) { res.locals.message = err.message; res.locals.error = req.app.get('env') === 'development' ? err : {}; res.status(err.status || 500); res.render('error');});module.exports = app;route: var express = require('express');var router = express.Router();var authorController = require('../controllers/authorController');authorController.findAuthorsByFirstAndLastName);router.get('/', function (req, res) { if(req.query.firstName||req.query.lastName) { res.send(authorController.findAuthorsByFirstAndLastName(req,res)); }else{ res.send(authorController.author_list(req,res)); } });module.exports = router;controller:var Author = require('../models/author')var async = require('async')exports.author_list = function(req, res, next) { Author.find({},function(err, authors) { if (err){ res.send(err); } return.json(authors); }); }; exports.findAuthorsByFirstAndLastName = function (req, res, next){ var query = {} if(req.query.firstName||req.query.lastName) { query = {$or:[{firstName:{$regex: req.query.firstName, $options: 'i'}}, {lastName:{$regex: req.query.lastName, $options: 'i'}}]} } else { return res.status(500).send({ error: 'Unable to parse data'}); } var firstName = req.body.firstName; var lastName = req.body.lastName; Author.find(query , function (err, authors) { if(err) { res.send(err); } res.json(authors); }); }; 解决方案 You get cannot set headers after they are sent when you have two res.[whatever]s in your route. So you have res.send(functionCallThatAlsoDoesRes.Send). That's what's causing the error.If you want a route to take multiple actions between the request and the response, you can write those as separate middlewares. Middlewares always take the arguments req, res, and next (a function that says to go to the next middleware in the list).So, you might write:authorController.findAuthorsByFirstAndLastName = function(req, res, next) { if (!(req.query.firstName || req.query.lastName)) { res.locals.getFullAuthorList = true return next() } else { const query = /* whatever */ Author.find(query, (err, authors) => { if (err) return next(err) res.locals.authors = authors next() }) }}authorController.author_list = function(req, res, next) { if (!res.locals.getFullAuthorList) return next() // if we already have authors we don't need to do anything Author.find({}, (err, authors) => { if (err) return next(err) res.locals.authors = authors next() })}Then in your route, you'd say:router.get('/', authorController.findAuthorsByFirstAndLastName, authorController.author_list, (req, res) => { res.json({ authors: res.locals.authors })})If you haven't seen res.locals before, it's just a property on the response object that is available for you to attach things to. It persists throughout the request/response cycle and is cleared for each new request. 这篇关于如何将从控制器返回的数据传递到Express'路由器?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！
