CODESAMPLE

Proxy - Scala

Proxy Scala

The Proxy pattern provides a surrogate or placeholder for another object to control access to it. This is useful for scenarios like remote access, security checks, or lazy initialization. Here, we have a RealImage that’s expensive to create. The ImageProxy acts as a stand-in, only loading the RealImage when display() is called. This delays the potentially costly operation until it’s actually needed. The Scala implementation leverages immutability and the lazy val keyword for efficient lazy initialization, fitting the functional style often preferred in Scala. The display method is the key interaction point, triggering the real image loading if it hasn’t happened yet.

trait Image {
  def display(): Unit
}

class RealImage(private val filename: String) extends Image {
  println(s"Loading image from $filename...")
  Thread.sleep(2000) // Simulate a long loading time
  def display(): Unit = println(s"Displaying image from $filename.")
}

class ImageProxy(private val filename: String) extends Image {
  private val realImage: RealImage = new RealImage(filename) // Create the real image only when needed

  def display(): Unit = {
    realImage.display()
  }
}

object ProxyExample {
  def main(args: Array[String]): Unit = {
    val imageProxy = new ImageProxy("high_resolution_image.jpg")
    imageProxy.display() // This will trigger the loading of the RealImage
    imageProxy.display() // Subsequent calls will use the already loaded image
  }
}