Node.js 错误：对象函数没有方法

Question

我刚刚开始接触 Node.js，并按照 Howtonode、express 和 mongod 上关于 Node.js 的精彩教程进行操作。但是，我似乎收到了一个错误，而评论中没有其他人评论过。最新评论是大约一个月前，所以代码可能已经过时了？

问题是，当我访问 http://localhost:3000/ 时，页面显示 Internal Server Error 并且在终端中，我收到以下错误消息。有谁知道发生了什么事吗？

这是错误消息：

TypeError: Object function (){} has no method 'findAll'
    at Router.<anonymous> (/Users/x/nodejs/howtonode/blog/app.js:30:18)
    at done (/Users/x/nodejs/howtonode/blog/node_modules/express/lib/router/index.js:250:22)
    at middleware (/Users/x/nodejs/howtonode/blog/node_modules/express/lib/router/index.js:244:9)
    at param (/Users/x/nodejs/howtonode/blog/node_modules/express/lib/router/index.js:227:11)
    at pass (/Users/x/nodejs/howtonode/blog/node_modules/express/lib/router/index.js:232:6)
    at Router._dispatch (/Users/x/nodejs/howtonode/blog/node_modules/express/lib/router/index.js:255:4)
    at Object.handle (/Users/x/nodejs/howtonode/blog/node_modules/express/lib/router/index.js:45:10)
    at next (/Users/x/nodejs/howtonode/blog/node_modules/express/node_modules/connect/lib/http.js:203:15)
    at Object.handle (/Users/x/nodejs/howtonode/blog/node_modules/stylus/lib/middleware.js:187:7)
    at next (/Users/x/nodejs/howtonode/blog/node_modules/express/node_modules/connect/lib/http.js:203:15)
TypeError: Object function (){} has no method 'findAll'
    at Router.<anonymous> (/Users/x/nodejs/howtonode/blog/app.js:30:18)
    at done (/Users/x/nodejs/howtonode/blog/node_modules/express/lib/router/index.js:250:22)
    at middleware (/Users/x/nodejs/howtonode/blog/node_modules/express/lib/router/index.js:244:9)
    at param (/Users/x/nodejs/howtonode/blog/node_modules/express/lib/router/index.js:227:11)
    at pass (/Users/x/nodejs/howtonode/blog/node_modules/express/lib/router/index.js:232:6)
    at Router._dispatch (/Users/x/nodejs/howtonode/blog/node_modules/express/lib/router/index.js:255:4)
    at Object.handle (/Users/x/nodejs/howtonode/blog/node_modules/express/lib/router/index.js:45:10)
    at next (/Users/x/nodejs/howtonode/blog/node_modules/express/node_modules/connect/lib/http.js:203:15)
    at Object.handle (/Users/x/nodejs/howtonode/blog/node_modules/stylus/lib/middleware.js:187:7)
    at next (/Users/x/nodejs/howtonode/blog/node_modules/express/node_modules/connect/lib/http.js:203:15)

app.js

var express = require('express');
var ArticleProvider = require('./articleprovider-memory').ArticleProvider;

var app = module.exports = express.createServer()

// Configuration
app.configure(function() {
    app.set('views', __dirname + '/views');
    app.set('view engine', 'jade');
    app.use(express.bodyParser());
    app.use(express.methodOverride());
    app.use(require('stylus').middleware({ src: __dirname + '/public' }));
    app.use(app.router);
    app.use(express.static(__dirname + '/public'));
});

app.configure('development', function() {
    app.use(express.errorHandler({ dumpExceptions: true, showStakc: true }));
});

app.configure('production', function() {
    app.use(express.errorHandler());
});

var articleProvider= new ArticleProvider();


// Routes
app.get('/', function(req, res) {
    ArticleProvider.findAll(function(error, docs) {
        res.send(docs);
    });
});

app.listen(3000);

article-provider-memory.js

var articleCounter = 1;

ArticleProvider = function(){};
ArticleProvider.prototype.dummyData = [];

ArticleProvider.prototype.findAll = function(callback) {
  callback( null, this.dummyData )
};

ArticleProvider.prototype.findById = function(id, callback) {
  var result = null;
  for(var i =0;i<this.dummyData.length;i++) {
    if( this.dummyData[i]._id == id ) {
      result = this.dummyData[i];
      break;
    }
  }
  callback(null, result);
};

ArticleProvider.prototype.save = function(articles, callback) {
  var article = null;

  if( typeof(articles.length)=="undefined")
    articles = [articles];

  for( var i =0;i< articles.length;i++ ) {
    article = articles[i];
    article._id = articleCounter++;
    article.created_at = new Date();

    if( article.comments === undefined )
      article.comments = [];

    for(var j =0;j< article.comments.length; j++) {
      article.comments[j].created_at = new Date();
    }
    this.dummyData[this.dummyData.length]= article;
  }
  callback(null, articles);
};

/* Lets bootstrap with dummy data */
new ArticleProvider().save([
  {title: 'Post one', body: 'Body one', comments:[{author:'Bob', comment:'I love it'}, {author:'Dave', comment:'This is rubbish!'}]},
  {title: 'Post two', body: 'Body two'},
  {title: 'Post three', body: 'Body three'}
], function(error, articles){});

exports.ArticleProvider = ArticleProvider;

Answer 1

这是 app.js 中 ArticleProvider 的大写形式：

// Routes
app.get('/', function(req, res) {
    ArticleProvider.findAll(function(error, docs) {
        res.send(docs);
    });
});

它应该是：

// Routes
app.get('/', function(req, res) {
    articleProvider.findAll(function(error, docs) {
        res.send(docs);
    });
});