persistent components

Persistent components are a way of nesting case classes inside of your persistent objects. They never get persisted on their own, but rather as part of some other persistent type in your domain model.

For example, let’s suppose we want to group the user’s firstName and lastName fields into a FullName case class:

import longevity.model.annotations.component
import longevity.model.annotations.persistent

@component[DomainModel]
case class FullName(
  firstName: String,
  lastName: String)

@persistent[DomainModel]
case class User(
  username: String,
  fullName: FullName)

Be sure to declare your component class in the same package as, or in a sub-package of, the package you declare your domain model. Assuming you don’t fabricate your own longevity.model.ModelEv[DomainModel], if you declare your component class in another package, you will get a compiler error - something about implicit model evidence not being found.

The @component[DomainModel] annotation creates a companion object that extends longevity.model.CType[DomainModel, FullName]. If FullName already has a companion object, it will be augmented to extend CType. The CType[DomainModel, FullName] will be used to help build the ModelType[DomainModel], which collects all the different parts of your model.

Here is the equivalent code without using annotations:

import longevity.model.CType

case class FullName(
  firstName: String,
  lastName: String)

object FullName extends CType[DomainModel, FullName]

You can put components in components, and components in collections, and collections in components. For example:

import longevity.model.annotations.component
import longevity.model.annotations.persistent

@component[DomainModel]
case class Email(email: String)

@component[DomainModel]
case class EmailPreferences(
  primaryEmail: Email,
  emails: Set[Email])

@component[DomainModel]
case class Address(
  street: String,
  city: String)

@persistent[DomainModel]
case class User(
  username: String,
  emails: EmailPreferences,
  addresses: Set[Address])