CODESAMPLE

Self-contained Systems - Scala

Self-contained Systems Scala

The Self-Contained System pattern aims to reduce dependencies by bundling all resources a component needs (configuration, data, etc.) within the component itself. This promotes portability, testability, and isolation. My Scala example demonstrates this by encapsulating the data and logic for a basic user profile within a UserProfile object, including a default configuration. Configuration is handled via a companion object for easy access and modification. No external configuration files or database connections are required—everything needed is available directly within the UserProfile itself. This is idiomatic Scala due to the strong emphasis on immutability with case class and the use of objects for singletons and associated data.

// UserProfile.scala
object UserProfile {
  // Default configuration – fully contained within the system
  case class Config(defaultName: String = "Anonymous", maxDisplayNameLength: Int = 30)

  val defaultConfig = Config()

  def apply(userId: Int, config: Config = defaultConfig): UserProfile = {
    new UserProfile(userId, config)
  }
}

case class UserProfile(userId: Int, config: UserProfile.Config) {
  private var _name: String = config.defaultName

  def name: String = _name

  def setName(newName: String): Unit = {
    val trimmedName = newName.take(config.maxDisplayNameLength)
    _name = trimmedName
  }

  override def toString: String = s"User ID: $userId, Name: $name"
}

object Main extends App {
  val user1 = UserProfile(1) // Uses default config
  println(user1)

  val customConfig = UserProfile.Config(defaultName = "Guest", maxDisplayNameLength = 15)
  val user2 = UserProfile(2, customConfig)
  user2.setName("Very Long Display Name")
  println(user2)
}