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/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