Add example for model relations

[kulakowka]

Can somebody show an example of creating relations between the models?

I want to relate a model Tutorial and Comment. How can i do that?

I make it so:

'use strict'

const Sequelize = require('sequelize')

module.exports = function (sequelize) {
  const comment = sequelize.define('comment', {
    content: {
      required: true,
      type: Sequelize.TEXT,
      allowNull: false
    },
    tutorialId: {
      required: true,
      type: Sequelize.INTEGER
    }
  }, {
    timestamps: true,
    freezeTableName: true
  })

  comment.belongsTo(sequelize.models.tutorial)

  comment.sync({
    force: true
  })

  return comment
}

But sometimes, when i start my application i have error:

Unhandled rejection SequelizeDatabaseError: relation "tutorial" does not exist

I used to work only with mongoDB. But I think I need to learn sequelize.

It would be great if we had more examples that show how to work with the database, how to set up the relationship between models and between services. I read the documentation, but it very much and I'm not like I can not configure it to work properly.

[kulakowka]

It seems I figured.

[ekryski]

This is more of a documentation issue but I've re-opened for visibility and created this issue to track actual progress: feathersjs-ecosystem/docs#51

[DesignByOnyx]

I am running into a similar issue as @kulakowka - I keep getting a SequelizeUniqueConstraintError: Validation Error when starting with an empty database. My code is nearly identical to kulakowka's, except in place of comment.belongsTo(sequelize.models.tutorial) I am doing the following because the tutorial does not exist yet:

const tutorial = sequelize.import( path.join(__dirname, "../tutorial/tutorial-model") );

... I'm not even calling .belongsTo yet - I'm just trying to import the model and I get the error. An example on how to set up relationships before the model is sync()'d would be great.

[silvestreh]

I'm kinda lost here… Disclaimer: I'm a total noob when it comes to SQL and relational databases, I have some experience with Mongo and, like @kulakowka, I want to learn some sequelize.

Say I have a model for a artists and another for events. Events can have many artists associated to it…

module.exports = function(sequelize) {
    const event = sequelize.define('events', {
        date: {
            type: Sequelize.DATE,
            defaultValue: Sequelize.NOW,
            allowNull: false
        },
        title: {
            type: Sequelize.STRING,
            allowNull: false
        }
    }, {
        freezeTableName: true
    });

    setImmediate(() => {
        // This is probably wrong, but otherwise most models are undefined
        // Also this, I believe, runs after event.sync() which might be a problem

        event.hasMany(sequelize.models.artists, { as: 'artists' });
    });

    event.sync();

    return event;
};

It's my understanding that { as: 'artists' } should create a column which can hold many integers (an array maybe?) referring to different artists; yet I fail to see this column showing up on my (empty) table.

Is there something I'm missing? I believe I would need to ALTER the table to add the column, would that happen automagically when I add a new event? I'm… well… confused and lost. I'm asking here because Sequelize's documentation doesn't quite match Feathers services approach.

[lopezjurip]

What's the correct way to do this?

[silvestreh]

@mrpatiwi the problem is using the sync() method right after the model definition. You could run sync only once inside server/src/services/index.js at the end of the file (and don't forget to remove the line that calls this method inside the model definition file)

I opted to create a new file server/src/services/relationships.js where I defined the relationships between models and then ran the sync() method.

EDIT: Please note that my experience with both Feathers and Sequelize is extremely limited and what I did is, in no way, recommended nor endorsed by the Feathers team. Hell, I'm not even sure what I did is considered a best practice or anything like that, it just made sense to me.

[ekryski]

I'm working on an example this evening.

[lopezjurip]

My current approach:

// src/services/organization/organization-model.js

const Sequelize = require('sequelize');

module.exports = function(sequelize) {
  const organization = sequelize.define('organization', {
    name: {
      type: Sequelize.STRING,
      allowNull: false,
    },
  }, {
    classMethods: {
      associate(models) {
        organization.hasMany(models.user);
      },
    },
  });

  return organization;
};

// src/services/index.js

const Sequelize = require('sequelize');

const authentication = require('./authentication');
const user = require('./user');
const organization = require('./organization');

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

  const sequelize = new Sequelize(app.get('postgres'), {
    dialect: 'postgres',
    logging: false, // console.log,
  });
  app.set('sequelize', sequelize);

  app.configure(authentication);
  app.configure(user);
  app.configure(organization);

  // Setup relationships
  const models = sequelize.models;
  Object.values(models)
    .filter(model => model.associate)
    .forEach(model => model.associate(models));

  sequelize.sync();
};

[ekryski]

@mrpatiwi solid. Very similar to @DesignByOnyx's solution he put over here.

[wojohowitz]

I would think @mrpatiwi approach is in line with the squelize cli generator, right?
I would personally would like migrations instead of sync().
Leveraging the sequelize cli could take care of that as well as seeders. Could all that be required is to have the generator create a .sequelizerc with the proper paths for config, migrations, and the model locations (noting that the model locations would be the trick as they are in their own service folders)?

[againer]

Thanks @mrpatiwi.

[DesignByOnyx]

FYI - the new generators will build all of the association code for you. Among other things it puts models in their own folder (de-coupled from services) and will generate the code which calls associate() on the model definitions. If you have a project with the old generators, then do not use the new ones. If you are starting a new project, try out the new ones. I have been using them with success. (pre release docs)

$ npm install feathers-cli@pre -g