Attributes can be calculated server-side by setting the attribute.value configuration property to a function.

collections:
  example_collection:
    attributes:
      current_date:
        value: (timestamp)

would set the current_date attribute, regardless of the value supplied by the client.

Combining attributes

By using the model or value parameters, this can also be used to combine several attributes.

collections:
  example_collection:
    attributes:
      first_name:
        type: string
      last_name:
        type: string
      name:
        value: (model.first_name + ' ' + model.last_name)

Transformations

It can also be used to transform or normalize the value supplied by the client.

When doing so, please keep in mind that value might be undefined, unless attribute.validate.required is true.

collections:
  example_collection:
    attributes:
      name:
        value: (value.toLowerCase())

would fail when the client sets name to undefined. Instead, this should be:

collections:
  example_collection:
    attributes:
      name:
        value: '(typeof value === "string" ? value.toLowerCase() : value)'