LoopBack Types - Loopback Next

Overview

When defining a model in LoopBack 4, property types are the important part. No matter whether it is for defining properties with decorator @property or defining a model at runtime, you may want to specify the types in the definition. The following is a typical property definition:

Defining a property with the decorator

@property({
  type: 'string',
  require: true,
  // other fields
})
userName: String;

Defining a model at runtime

const UserDef = new ModelDefinition('User')
  .addProperty('id', {type: 'number', id: true})
  .addProperty('userName', {type: 'string'});

The following table summarizes LoopBack types.

<table> <tbody> <tr> <th>Type</th> <th>Description</th> <th>Example</th> </tr> <tr> <td>any</td> <td>Any type, including array, object, Date, or GeoPoint</td> <td>Any of: <code>true</code>, <code>123</code>, <code>"foo"</code>, <code>[ "one", 2, true ]</code></td> </tr> <tr> <td>array</td> <td> JSON array See <a href="LoopBack-types.html#array-types">Array types</a> below. </td> <td><code>[ "one", 2, true ]</code></td> </tr> <tr> <td>Boolean</td> <td>JSON Boolean</td> <td><code>true</code></td> </tr> <tr> <td>buffer</td> <td>Node.js <a href="http://nodejs.org/api/buffer.html" class="external-link" rel="nofollow">Buffer object</a></td> <td> <pre>new Buffer(42);</pre> </td> </tr> <tr> <td>date</td> <td>JavaScript <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date" class="external-link" rel="nofollow">Date object</a></td> <td> <code>new Date("December 17, 2003 03:24:00");</code> </td> </tr> <tr> <td>GeoPoint</td> <td> LoopBack <a href="http://apidocs.loopback.io/loopback-datasource-juggler/#geopoint" class="external-link" rel="nofollow">GeoPoint</a> object </td> <td> <pre>new GeoPoint({lat: 10.32424, lng: 5.84978});</pre> </td> </tr> <tr> <td>Date</td> <td> LoopBack<a href="http://apidocs.loopback.io/loopback-datasource-juggler/#datestring" class="external-link" rel="nofollow"> DateString</a> object </td> <td> <code>"2000-01-01T00:00:00.000Z"</code> <code>"2000-01-01"</code> <code>"2000-01-01 12:00:00"</code> </td> </tr> <tr> <td>null</td> <td>JSON null</td> <td><code>null</code></td> </tr> <tr> <td>number</td> <td>JSON number</td> <td> <code>3.1415</code> </td> </tr> <tr> <td>Object</td> <td> JSON object or any type See <a href="LoopBack-types.html#object-types">Object types</a> below. </td> <td> <pre class="de1">{ "userName": "John89", "age": 25, "vip": false}</pre> </td> </tr> <tr> <td>String</td> <td>JSON string</td> <td><code>"LoopBack"</code></td> </tr> </tbody> </table>

In general, a property will have undefined value if no explicit or default value is provided.

{% include tip.html content=" The type name is case-insensitive; so for example you can use either "Number" or "number". " %}

{% include note.html content="GeoPoint is not supported. See GitHub issue #1981" %}

Array types

The following are examples of how you can define array type properties:

  @property({
    type: 'array',
    itemType: 'string',
    length: 20,
  })
  strAry?: string[]; // e.g ['can', 'only', 'contain', 'strings']

  @property({
    type: 'array',
    itemType: 'number',
  })
  numAry?: number[]; // e.g [42, 998, 1]

  @property({
    type: 'array',
    itemType: 'any',
  })
  anyAry?: any[]; // e.g ['LoopBack', 4, true]

  @property({
    type: 'array',
    itemType: 'object',
  })
  ObjAry?: object[]; // e.g [{'Nodejs': 'LoopBack'}]

Object types

Use the Object type when you need to be able to accept values of different types, for example a string or an array.

A model often has properties that consist of other properties. For example, the user model can have an address property that is in type Address, which has properties street, city, state, and zipCode:

@model()
export class Address extends Entity {
  @property({
    type: 'number',
  })
  id: number;

  // street, city, state, zipCode proper definitions ..
}

@model()
export class User extends Entity {
  // other props

  @property({
    type: 'object',
  })
  address: Address;
}

The value of the address is the definition of the Address type.

{% include important.html content=" The User model has to reference the Address model." %}