Class Model

Model extends from your ORM's Model native model class(eg:- for Sequelize, sequelize.Model) and hence have all the features and behaviors included in the ORM's model class.

As an example, say that the Customer Model class is associated with the customer table. This would mean that the class's name attribute is automatically mapped to the name column in customer table. Thanks to Model, assuming the variable customer is an object of type Customer, to get the value of the name column for the table row, you can use the expression customer.name. In this example, Model is providing an object-oriented interface for accessing data stored in the database. But Model provides much more functionality than this.

All the models used for Pwoli components should be extended from Model

To declare a Model class you need to extend Model

class Customer extends Model
{
     static associate() { // your model relations
         Customer.hasMany(Order, { as: 'orders', foreignKey: 'customerId' });
         ...
     }
     ...
     // your additional implementations here..
     ...
}

Important Note: If your ORM is Sequelize, you should perform additional steps like defining the model attributes and options for initializing each model like below:

const attributes = {
   id: {
       type: DataTypes.INTEGER,
       allowNull: false,
       defaultValue: null,
       primaryKey: true,
       autoIncrement: true,
   email: {
       type: DataTypes.STRING(255),
       allowNull: false,
       defaultValue: null,
       primaryKey: false,
       autoIncrement: false,
       comment: null,
       field: 'email',
       validate: {
           isEmail: { msg: "Please enter a valid Email" },
       },
   ...
   },
  };
  const options = {
       tableName: 'Customer',
       comment: '',
       sequelize,
       hooks: {},
  };
  Customer.init(eventAttributes, eventOptions);
  Customer.associate(); //for associating relations like `hasOne`, `hasMany` etc.

Class instances are obtained in one of two ways:

• Using the new operator to create a new, empty object
• Using a method to fetch an existing record (or records) from the database

Below is an example showing some typical usage of Model:

let user = new User();
user.name = 'Mahesh';
await user.save();  // a new row is inserted into user table

// the following will retrieve the user 'Mahesh' from the database
let user = await User.findOne({where: {name: 'Mahesh'});

// this will get related records from orders table when relation is defined. Please note that you need to `include` the required relations like below:
let user = await User.findOne({where: {name: 'Mahesh'}, include: [{ model: Order, as: 'orders' }]);
let orders = user.orders;

If your ORM is Sequelize, please refer https://sequelize.org/master/manual/model-basics.html