Attribute

Attribute is used for decorating direct model properties. It takes one argument, AttributeOptions, the type and the default values can be checked here.

Options

• useClass: boolean | class | () => class

  • optional
  • when omitted, the property value from the response will directly be used as a value of decorated model property
  • when true, an instance of property type class will be used as a value of decorated model property. While instantiating an instance of type class, the raw value of the property from the response will be passed as a first parameter to the constructor
  • when string, the class will be searched in DatastoreService.modelTypes based on modelType (see DefiningModelRelationships)
  • when function, the function will be called and it is expected of function to return a class which should be instantiated
  • when instance of SimpleHalModel or HalModel, the value of useClass property will be used as a class for instantiating the property value. While instantiating an instance of type class, the raw value of the property from the response will be passed as a first parameter to the constructor

• transformResponseValue: (rawAttribute: any) => any

  • optional
  • when provided, the raw property value from the response is passed to transformResponseValue function and returned value is saved to the model (instead of raw value from the response).

• transformBeforeSave: (rawAttribute: any) => any

  • when provided, the model property value is passed to the transformResponseValue function and returned value is used while creating a payload for the request

• externalName: string

  • if your model property name and the property name fetched from the server are different, you can specify the external property name setting this property
  • this name will be used when parsing a response from server and also when generating a payload for sending it to the server

• excludeFromPayload: boolean

  • optional
  • default: false
  • if true, the property won't be included in the payload of PUT/POST requests

Example

Raw response fetched from the server

GET /User/1

{
  "id": "1",
  "name": "John",
  "additionalInfo": {
    "height": "170",
    "weight": "75"
  }
},
...

We have an additional class for additionalInfo property:

class AdditionalUserInfo {
  constructor(private userData) {}

  get height() {
    return this.userData.height;
  }
}

Case 1

class User extends HalModel {
  @Attribute()
  public name: string;

  @Attribute()
  public additionalInfo: AdditionalUserInfo;
}

While parsing the user response, under the hood, user.additionalInfo = rawResponse.additionalInfo will be performed on the instance of a user model which means that user.additionalInfo will be a simple object.

Case 2

class User extends HalModel {
  @Attribute()
  public name: string;

  @Attribute({
    useClass: true
  })
  public additionalInfo: AdditionalUserInfo;
}

While parsing the user response, under the hood, user.additionalInfo = new AdditionalUserInfo(rawResponse.additionalInfo) will be performed on the instance of a user model which means that user.additionalInfo will be an instance of AdditionalUserInfo class. In this case AdditionalUserInfo must extend SimpleHalModel,

class AdditionalUserInfo extends SimpleHalModel{}

Case 3

class SomeInfo {}

class User extends HalModel {
  @Attribute()
  public name: string;

  @Attribute({
    useClass: () => SomeInfo
  })
  public additionalInfo: AdditionalUserInfo;
}

While parsing the user response, under the hood, user.additionalInfo = new SomeInfo(rawResponse.additionalInfo) will be performed on the instance of a user model which means that user.additionalInfo will be an instance of SomeInfo class.

Case 4

class SomeInfo extends SimpleHalModel {}

class User extends HalModel {
  @Attribute({
    useClass: SomeInfo
  })
  public additionalInfo: AdditionalUserInfo;
}

The behaviour of this case is the same as in Case #3. The difference is that instead of providing a function to useClass, a concreate class is provided. The provided class must extend SimpleHalModel.