Loopback Component for Extending Built-in Model

A component to extend Loopback built-in Model (User, AccessToken, etc.) without creating new Model. loopback-component-extender will loads Model extension synchronously.

Features

1. Extend built-in model definition:
   • acl
   • hidden
   • mixins
   • options
   • properties
   • relations (Polymorphic and HasAndBelongsToMany is not supported yet)
   • Datasource-related options (e.g. mysql)

Usage

Steps below is an example to extend User model:

1. Create model file user-x.js and user-x.json in common/models folder.
2. Write only attributes to be extended in user-x.json such as mapping model to MySQL table, add properties, add relations, etc. No need to rewrite what already defined in User model, unless you need it:

   {
     "mysql": {
       "table": "user"
     },
     "properties": {
       "emailVerified": {
         "type": "boolean",
         "mysql": {
           "columnName": "email_verified",
           "dataType": "smallint",
           "dataLength": null,
           "dataPrecision": 1,
           "dataScale": 0,
           "nullable": "N"
         }
       },
       "verificationToken": {
         "type": "string",
         "mysql": {
           "columnName": "verification_token",
           "dataType": "smallint",
           "dataLength": null,
           "dataPrecision": 1,
           "dataScale": 0,
           "nullable": "Y"
         }
       },
       "createdAt": {
         "type": "Date",
         "required": false,
         "mysql": {
           "columnName": "created_at",
           "dataType": "datetime",
           "nullable": "N"
         }
       },
       "updatedAt": {
         "type": "Date",
         "required": false,
         "mysqlz": {
           "columnName": "updated_at",
           "dataType": "datetime",
           "nullable": "N"
         }
       }
     },
     "mixin": {
       "Controller": true
     },
     "relations": {
       "customer": {
         "type": "hasOne",
         "model": "Customer",
         "foreignKey": "customerId"
       },
     }
   }

3. Write extended methods in user-x.js file.

   module.exports = User => {
     const say = User.say = (userId, message) => {
       console.log('User %d said %s', userId, message)
     }
   
     User.prototype.say = function(message) => {
       let userId = this.id
       say(userId, message)
     }
   }

4. Enable component in component-config.json

   {
     "loopback-component-extender": {
       "models": "User"
     }
   }

TODOs

• [ ] Add support for extending Polymorphic and HasAndBelongsToMany relation
• [ ] API documentation
• [ ] Write test

Related Works

• loopback-controller-mixin - Separate remote method from Model file and hides pre-defined remote method

Contributors

• Saggaf Arsyad [email protected]