Sequelize cyclic dependency

Question

This is my User model

'use strict';
var bcrypt = require('bcrypt');

module.exports = function(sequelize, DataTypes) {
  var User = sequelize.define('User', {
    email: {
      type: DataTypes.STRING,
      validate: {
        isEmail: true,
        notEmpty: true,
        notNull: false
      },
      unique: true
    },

    password: DataTypes.STRING,
    name: DataTypes.STRING,

    username: {
      type: DataTypes.STRING,
      unique: true
    },

    admin: DataTypes.BOOLEAN,

    googleId: DataTypes.BOOLEAN

  }, {
    classMethods: {
      associate: function(models) {
        User.hasMany(models.Award);
        User.hasMany(models.Media);
        User.hasMany(models.Comment);
        User.hasMany(models.Like);
        User.hasMany(models.CheckIn);
      }
    }
  });


  return User;
};

and this is my Media model:

'use strict';

module.exports = function(sequelize, DataTypes) {
  var Media = sequelize.define('Media', {

    type: DataTypes.ENUM('photo', 'video'),
    description: DataTypes.STRING,

    url: DataTypes.STRING,

    gps: DataTypes.GEOMETRY('POINT')

  }, {
    classMethods: {
      associate: function(models) {
        //Media.belongsTo(models.Event);
        //Media.belongsTo(models.User);
        Media.hasMany(models.Comment);
        Media.hasMany(models.Like);
      }
    }
  });


  return Media;
};

And I'm getting this error:

Unhandled rejection Error: Cyclic dependency found. Users is dependent of itself.
Dependency chain: Awards -> Users -> Media => Users

Previously I had a cyclic dependency and it's now removed but sequelize still throws this error. Why is this happening?

If I remove the User.hasMany(models.Media) association the error will disappear. But why is it still happening when the Media model has no reference to the User model?

Answer 1

Settings constraints: false will work, but will not create the foreign key in your DB.

If all your db access is done from sequelize, that can be an acceptable solution. But if you access your DB in several ways, that becomes complicated to handle. E.g: Hasura does not create relationships between models.

The real issue is that sequelize is not smart enough to create the table in 2 steps. Other ORMs handle that by first creating the tableA without the foreign key, create the tableB with foreignKey to tableA, and alter TableA to create foreign key to tableB.

So the solution is to add constraints: false to your User.hasMany(models.Media) then create then run foreign key constrain.

    const addMediaUserForeignKey = queryInterface.addConstraint(
      'Media', {
        type: 'foreign key',
        onUpdate: 'CASCADE',
        onDelete: 'CASCADE',
        references: {
          table: 'User',
          field: 'id',
        },
        fields: [ 'userId' ]
      }
    ).catch((e) => {})

Answer 2

Consider using hasMany as follows:

User.hasMany(models.Award, {as: 'ifYouWantAlias', constraints: false, allowNull:true, defaultValue:null});

note that you don't need the following part but it makes it clearer in my opinion.

allowNull:true, defaultValue:null

It is explained well in here: http://docs.sequelizejs.com/en/latest/api/associations/