Node.js 续集和羽毛：当关系破裂时

在花了两天的时间试图弄明白为什么我的Sequelize模特们不致力于他们的关系之后，我决定是时候向你们大家征求意见了

故事是这样的

我正在使用Postgres（9.4）数据库编写Feathers JS应用程序，并使用Sequelize作为驱动程序。我在中运行了安装程序，经过一些劝说，我让迁移运行起来

据我所知，在使用Sequelize时必须特别考虑双向关系，因为如果

ModelA

references

ModelB

，

ModelB

必须已经定义，但是如果

ModelB

references

ModelA

…那么，我们会遇到一个依赖循环

这是因为依赖循环，文档说“使用这里描述的方法定义您的模型”。（好的，从技术上来说，它只是“假设”使用了这样的结构。另外，我只能发布2个链接，否则我会链接那个笨蛋。对此我很抱歉。）我在一个文档中发现了相同的结构

当然，我反映了所有这些（当然，除非我遗漏了一个小但重要的细节），但是……仍然没有骰子

以下是我所看到的：

迁移 迁移/create-accounts.js 迁移/create-users.js psql 然后我启动了psql以查看引用是否正确：

databaseName=#\d账户

：

Referenced by:
    TABLE "users" CONSTRAINT "users_accountId_fkey" FOREIGN KEY ("accountId") REFERENCES accounts(id)

databaseName=#\d用户

：

Foreign-key constraints:
    "users_accountId_fkey" FOREIGN KEY ("accountId") REFERENCES accounts(id)

到目前为止还不错，对吧

让我们看看这个节目的模特部分

模型 src/models/account.js src/models/user.js src/models/index.js 齐心协力 src/app.js 为了简洁起见，我在

app

中加载了很多模型，如下所示：

const models = require('./models')
app.use(compress())
  // Lots of other statements
  .configure(models);

测试 我一直在尝试制作一个用于更改密码、修改用户权限和其他实用程序任务的命令行实用程序，因此我采用了Vorpal（同样，只有2个链接，因此如果不熟悉，您必须自己查找——对不起）。以下是我的Vorpal程序的相关片段：

cli.js 啊

但是，如果我取消对

User.findOne（）

上方的行的注释，它就像一个符咒

为什么我必须在查询关系之前立即显式设置关系？为什么在用户模型的associate（）方法中建立的关系（可能）没有保持不变？据我所知，它被调用了，而且是在正确的模型上。它是否以某种方式被推翻？由于某种奇怪的原因，

app

，在用户模型中进行关联时是否与

cli.js

中的不一样

---

我真的很困惑。非常感谢你们所能给予的任何帮助。

我不知道为什么会这样，但我确实通过以下更改使其发挥了作用

src/models/index.js 我在导出函数末尾附近注释掉了以下区块：

Object.keys(sequelize.models).forEach(modelName => {
  if ('associate' in sequelize.models[modelName]) {
    sequelize.models[modelName].associate();
  }
});

然后我将其移动到

src/relate models.js

：

src/relate-models.js 在

src/app.js

中，我调用了该函数并。。。普雷斯托改变了，成功了

src/app.js` 结束。如果有人能解释为什么以后做同样的事情会奏效，请告诉我，但现在…它奏效了

'use strict';

// account-model.js - A sequelize model
//
// See http://docs.sequelizejs.com/en/latest/docs/models-definition/
// for more of what you can do here.

const Sequelize = require('sequelize');

module.exports = function(app) {
  // We assume we're being called from app.configure();
  // If we're not, though, we need to be passed the app instance.
  // Fair warning: I added this bit myself, so it's suspect.
  if (app === undefined)
    app = this;
  const sequelize = app.get('sequelize');

  // The rest of this is taken pretty much verbatim from the examples
  const account = sequelize.define('account', {
    id: {
      type: Sequelize.INTEGER,
      primaryKey: true,
      autoIncrement: true
    },
    name: Sequelize.STRING,
    url_name: Sequelize.STRING,
  }, {
    paranoid: true,
    timestamps: true,

    classMethods: {
      associate() {
        const models = app.get('models');
        this.hasMany(models['user'], {});
      }
    }
  });

  return account;
};

'use strict';

// user-model.js - A sequelize model
//
// See http://docs.sequelizejs.com/en/latest/docs/models-definition/
// for more of what you can do here.

const Sequelize = require('sequelize');

module.exports = function(app) {
  // We assume we're being called from app.configure();
  // If we're not, though, we need to be passed the app instance
  if (app === undefined)
    app = this;
  const sequelize = app.get('sequelize');

  const user = sequelize.define('user', {
    id: {
      type: Sequelize.INTEGER,
      primaryKey: true,
      autoIncrement: true
    },
    accountId: {
      type: Sequelize.INTEGER,
      references: {
        model: 'accounts', // Table name...is that right? Made the migration work...
        key: 'id'
      }
    },
    email: Sequelize.STRING,
    [... curtailed for brevity ...]
  }, {
    // Are these necessary here, or just when defining the model to make a
    //  psuedo-migration?
    paranoid: true, // soft deletes
    timestamps: true,

    classMethods: {
      associate() {
        const models = app.get('models');
        // This outputs like I'd expect:
        // Just to be sure...From the user model, models["account"]: account
        console.log('Just to be sure...From the user model, models["account"]:', models['account']);
        this.belongsTo(models['account'], {});
      }
    }
  });

  return user;
};

// I blatantly ripped this from both the following:
// https://github.com/feathersjs/generator-feathers/issues/94#issuecomment-204165134
// https://github.com/feathersjs/feathers-demos/blob/master/examples/migrations/sequelize/src/models/index.js

const Sequelize = require('sequelize');
const _ = require('lodash');

// Import the models
const account = require('./account');
const user = require('./user');

module.exports = function () {
  const app = this;

  // Note: 'postgres' is found in config/default.json as the db url
  const sequelize = new Sequelize(app.get('postgres'), {
    dialect: app.get('db_dialect'),
    logging: console.log
  });
  app.set('sequelize', sequelize);

  // Configure the models
  app.configure(account);
  app.configure(user);

  app.set('models', sequelize.models);

  // Set associations
  Object.keys(sequelize.models).forEach(modelName => {
    if ('associate' in sequelize.models[modelName]) {
      sequelize.models[modelName].associate();
    }
  });

  sequelize.sync();

  // Extra credit: Check to make sure the two instances of sequelize.models are the same...
  // Outputs: sequelize.models after sync === app.get("models")
  // I've also run this comparison on sequelize and app.get('sequelize'); _.eq() said they also were identical
  if (_.eq(sequelize.models, app.get('models')))
    console.log('sequelize.models after sync === app.get("models")');
  else
    console.log('sequelize.models after sync !== app.get("models")');
};

const models = require('./models')
app.use(compress())
  // Lots of other statements
  .configure(models);

const vorpal = require('vorpal')();
const _ = require('lodash');

// Initialize app
// This seems a bit overkill since we don't need the server bit for this, but...
const app = require('./src/app');
const models = app.get('models');

// Get the models for easy access...
const User = models['user'];
const Account = models['account'];

// Run by issuing the command: node cli test
// Outputs to terminal
vorpal.command('test', 'A playground for testing the Vorpal environment.')
  .action(function(args, callback) {
    // User.belongsTo(Account); // <-- uncomment this and it works
    User.findOne({ include: [{ model: Account }]}).then((user) => {
      console.log("user.account.name:", user.account.name);
    });
  });

vorpal.show().parse(process.argv);

Just to be sure...From the user model, models["account"]: account
sequelize.models after sync === app.get("models")
connect: 
Unhandled rejection Error: account is not associated to user!
    at validateIncludedElement (/vagrant/node_modules/sequelize/lib/model.js:550:11)
    at /vagrant/node_modules/sequelize/lib/model.js:432:29
    at Array.map (native)
    at validateIncludedElements (/vagrant/node_modules/sequelize/lib/model.js:428:37)
    at .<anonymous> (/vagrant/node_modules/sequelize/lib/model.js:1364:32)
    at tryCatcher (/vagrant/node_modules/bluebird/js/release/util.js:16:23)
    at Promise._settlePromiseFromHandler (/vagrant/node_modules/bluebird/js/release/promise.js:504:31)
    at Promise._settlePromise (/vagrant/node_modules/bluebird/js/release/promise.js:561:18)
    at Promise._settlePromise0 (/vagrant/node_modules/bluebird/js/release/promise.js:606:10)
    at Promise._settlePromises (/vagrant/node_modules/bluebird/js/release/promise.js:685:18)
    at Async._drainQueue (/vagrant/node_modules/bluebird/js/release/async.js:138:16)
    at Async._drainQueues (/vagrant/node_modules/bluebird/js/release/async.js:148:10)
    at Immediate.Async.drainQueues (/vagrant/node_modules/bluebird/js/release/async.js:17:14)
    at runCallback (timers.js:574:20)
    at tryOnImmediate (timers.js:554:5)
    at processImmediate [as _immediateCallback] (timers.js:533:5)

Object.keys(sequelize.models).forEach(modelName => {
  if ('associate' in sequelize.models[modelName]) {
    sequelize.models[modelName].associate();
  }
});

/**
 * This is workaround for relating models.
 * I don't know why it works, but it does.
 *
 * @param app  The initialized app
 */
module.exports = function(app) {
  const sequelize = app.get('sequelize');

  // Copied this from src/models/index.js
  Object.keys(sequelize.models).forEach(modelName => {
    if ('associate' in sequelize.models[modelName]) {
      sequelize.models[modelName].associate();
    }
  });
}

const models = require('./models')
app.use(compress())
  // Lots of other statements
  .configure(models);

require('./relate-models')(app);