Sequelize migrations - node.js

Question

I am new to Sequelize and would like to know if anyone knows if there is a way to avoid the code duplication in Sequelize when using the migration functionality?
What I mean is that in the migration you would have something like this:
//migration-xyz.js
module.exports = {
up: function(migration, DataTypes, done) {
migration.createTable('Users',
{
name: DataTypes.STRING,
surname: DataTypes.STRING
});
},
down: function(migration, DataTypes, done) {
// logic for reverting the changes
}
}
But then the model would look something like this:
//user.js
module.exports = function(sequelize, DataTypes) {
var User = sequelize.define('User', {
name: DataTypes.STRING,
surname: DataTypes.STRING
});
return User;
};
Is there a way to get rid of the code duplication?
Thanks for the help! :)

Answer 1

As #WiredPrairie referenced in his/her comment, migrations and the attributes on a model are distinct things. Often we will create a model that has certain attributes and the associated migration to create the corresponding table. Later on more attributes will be added to the model and we will need to create a migration that adds columns for just the new attributes.
A way to remove the duplication would be to use sequelize.sync which creates your database from the model files. This has downsides though and should not be used on complex applications that are being deployed in different environments.
Maybe in the future the sequelize-cli will have a create:migration --model [modelfile] option where it will create the table for the corresponding model. This would have the same "duplication" of code but would make things a little faster.

Answer 2

When you initially ran the migrations via sequelize-cli
it set up the folder structure as:
-config
-config/config.json
-migrations
-models
-models/index.js
If you make sure your model file:
//user.js
module.exports = function(sequelize, DataTypes) {
var User = sequelize.define('User', {
name: DataTypes.STRING,
surname: DataTypes.STRING
});
return User;
};
is in the models directory, it will automatically be picked up when you
require('./models');
So, I've used the following code to import the new models for that revision of the migration:
//migrations-xyz.js
var Models = require('../models');
module.exports = {
up: function (queryInterface, Sequelize) {
/*
Add altering commands here.
Return a promise to correctly handle asynchronicity.
Example:
return queryInterface.createTable('users', { id: Sequelize.INTEGER});
*/
var tables = _.map(Models.sequelize.models, function(def){
var model = Models[def],
options = model.options,
tableName = model.tableName,
attributes = model.tableAttributes;
return queryInterface.createTable(tableName, attributes, options);
});
return Promise.all(tables);
},
down: function (queryInterface, Sequelize) {
/*
Add reverting commands here.
Return a promise to correctly handle asynchronicity.
Example:
return queryInterface.dropTable('users');
*/
return Models.sequelize.drop({logging: true});
}
};