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

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

or Yarn

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

Server configuration

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

`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.

$3

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

Now you can query for distinct values this way:

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

Or using promise:

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

$3

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:

`json
{
"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.

$3

#### Call distinct values with filter.

``js
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

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

Using default property and a filter:

``js
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

``js
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

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

Execute tests

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

Credits

Developed by
Juan Costa
for
ALIA Technologies