models.md

Models

Documentation on loopback Doc (https://loopback.io/doc/en/lb3/Defining-models.html)

Create new model

• with model generator :

  lb model MyModel

• manuel via documentation (https://loopback.io/doc/en/lb3/Model-definition-JSON-file.html)

Attach new model to datasource

• Edit file server/model-config.json and add

  "MyModel": {
    "dataSource": "[myDataSource]"
  },

database schema update

for create or update BDD schema with this new model, you can add you model on this file server/component-config.json

"loopback-component-auto-migrate": {
    ...
    "models": [
      ...
      "MyModel"
    ]
  }

Expose model on REST API

You must expose via REST with edit file server/model-config.json

  "MyModel": {
    "public": true
  },

You can visualize new REST endpoint on Swagger

Relations

see documentation

• many-to-one => belongsTo

// road.json
"relations": {
    "city": {
      "type": "belongsTo",
      "model": "City",
      "foreignKey": "cityCode"
    }
  },

• one-to-many => hasMany

// city.json
"relations": {
    "roads": {
      "type": "hasMany",
      "model": "Road",
      "foreignKey": "cityCode"
    }
  },

Mixins

Mixin is like 'hook' for add logic on Listener Models. see documentation (https://loopback.io/doc/en/lb3/Operation-hooks.html)

• Example of common models mixin

common/mixins.integrity-checks.js, this mixin verify constraint on relations.

You can active for a model with add this lines on your my-model.json

  ...
  "mixins": {
    "IntegrityCheck": {}
  },
  ...

• Example of custom model mixin

common/models.city.js

module.exports = function (City) {

  City.observe('before save', (ctx, next) => {
    if (ctx.instance) {
      ctx.instance.nameMin = ctx.instance.name.toLowerCase();
    } else {
      ctx.data.nameMin = ctx.data.name.toLowerCase();
    }
    next();
  });
};

ACL model

• edit file common/models/my-model.json
• add elements on section ACL (see doc)
• Sample

"acls": [      
    {  // All action Deny for All   
      "accessType": "*",
      "principalType": "ROLE",
      "principalId": "$everyone",
      "permission": "DENY"
    },
    { // Read action Allow for 'agent' role   
      "accessType": "READ",
      "principalType": "ROLE",
      "principalId": "agent",
      "permission": "ALLOW"
    },
    { // Read/Write action Allow for 'admin' role  
      "accessType": "*",
      "principalType": "ROLE",
      "principalId": "admin",
      "permission": "ALLOW"
    }
    ...
  ],