Loopback Distinct mixin for MongoDB

Provide to models the ability to query distinct values from database

This is a Loopback mixin to be used together with MongoDB connector. Works for Loopback 2 and 3.

How to install

Install the package through NPM

npm i -S @aliatech/loopback-mongo-distinct-mixin

or Yarn

yarn add --prod @aliatech/loopback-mongo-distinct-mixin

Server configuration

Include the mixin in server/model-config.json:

{
  "_meta": {
    "sources": [
      "loopback/common/models",
      "loopback/server/models",
      "../common/models",
      "./models"
    ],
    "mixins": [
      "loopback/common/mixins",
      "../node_modules/@aliatech/loopback-mongo-distinct-mixin/lib",
      "../common/mixins"
    ]
  }
}

Usage

Enable the mixin in your model definition, ie person.json.

Basic configuration

{
  "name": "Person",
  "properties": {
    "name": "string",
    "company": "string"
  },
  "mixins": {
    "Distinct": true
  }
}

Now you can query for distinct values this way:

app.models.Person.distinctValues('name', (err, names) => {
  if (err) return next(err);
  // names = ['john', 'mary', 'anne', ...]
});

Or using promise:

app.models.Person.distinctValues('name')
  .then((names) => {
    // names = ['john', 'mary', 'anne', ...]
  })
  .catch((err) => {
    // handle an error
  });

Advanced configuration

Enable the mixin passing an options object instead of just true.

These are the available options:

Option	Type	Required	Description
defaultProperty	string	optional	Default property name to get values. With this option, it won't be required to specify property argument.
remote	object	optional	Customize a remote method to call distinct feature.
remote.enabled	boolean	optional	Enable a remote method for distinctValues. (default false)
remote.name	string	optional	Name of the remote method. (default 'distinctValues')
remote.definition	object	optional	The Loopback definition of the remote method.

Default options

These are the default options that will be merged with the model specifics:

{
  "remote": {
    "enabled": false,
    "name": "distinctValues",
    "definition": {
      "description": "Find objects with distinct property",
      "http": {
        "path": "/distinctValues",
        "verb": "get"
      },
      "accepts": [{
        "arg": "property",
        "type": "string",
        "required": true
      }, {
        "arg": "where",
        "type": "object",
        "required": false
      }],
      "returns": {
        "arg": "objects",
        "type": "array",
        "root": true
      }
    }
  }
}

Note that property argument will required only if defaultProperty is not set.

Advanced usage

Call distinct values with filter.

app.models.Person.distinctValues('name', {company: 'alia'}, (err, names) => {
  // Got distinct names for objects having company = 'alia'
});

Note: Filter should be MongoDB native, not Loopback

Call distinct values using a default property.

1. Configure defaultProperty option
2. Call distinctValues omitting property argument

app.models.Person.distinctValues((err, names) => {
  // Do something
});

Using default property and a filter:

app.models.Person.distinctValues({company: 'alia'}, (err, names) => {
  // Do something
});

Remote distinctValues

1. Configure remote.enabled option to be true
2. Call through the API

const request = require('request');

request('http://localhost:3000/api/Person/distinctValues',
  {qs: {property: 'name', where: {company: 'alia'}}},
  (err, res, body) => {
    if (err) return next(err);
    if (res.statusCode === 200){
      const names = JSON.parse(body);
      // Do something
    }
});

Testing

Install develop dependences

npm i -D # If you use NPM
yarn install # If you use Yarn

Execute tests

npm test # Without coverage check
npm run test-with-coverage # With coverage check

Credits

Developed by Juan Costa for ALIA Technologies