Design Pattern Examples in Scala

Model and code examples of GoF Design Patterns for Scala.
This project is available for the following objectives:

• To understand GoF Design Pattern examples in Scala.
• To understand the mapping between UML model and Scala code.
• To try Model-Driven Development (MDD) using Astah and M PLUS plug-in.

UML model example:

Scala code example:

// ˅
package structuralPatterns.composite

// ˄

class File(_name: String, _size: Int) extends FileSystemElement {
  // ˅
  
  // ˄

  private val name: String = _name

  private val size: Int = _size

  override def getName(): String = {
    // ˅
    name
    // ˄
  }

  override def getSize(): Int = {
    // ˅
    size
    // ˄
  }

  // Print this element with the "upperPath".
  override def print(upperPath: String): Unit = {
    // ˅
    println(f"$upperPath/$this")
    // ˄
  }

  // ˅
  
  // ˄
}

// ˅

// ˄

Installation

UML Modeling Tool

• Download the modeling tool Astah UML or Professional, and install.
• Download M PLUS plug-in ver.2.7.6 or higher, and add it to Astah.
  How to add plugins to Astah

Scala Development Environment

• Install Java SDK 11 or higher.
• Install IntelliJ. Then, install Scala and SBT plugin in IntelliJ.

Usage

Code Generation from UML

1. Open the Astah file (model/DesignPatternExamplesInScala.asta).
2. Select model elements on the model browser of Astah.
3. Click the Generate Code button.
   
   The generated code has User Code Area. The User Code Area is the area enclosed by "˅" and "˄". Handwritten code written in the User Code Area remains after a re-generation. View code example.
   For detailed usage of the tools, please see Astah Manual and M PLUS plug-in Tips.

Build and Run

1. Open the project root directory (design-pattern-examples-in-scala) in IntelliJ.
2. Open Main.scala for the pattern you want to run, and click Run icon in the left gutter.

References

• Gamma, E. et al. Design Patterns: Elements of Reusable Object-Oriented Software, Addison-Wesley, 1994
• Hiroshi Yuki. Learning Design Patterns in Java [In Japanese Language], Softbank publishing, 2004

Licence

This project is licensed under the Creative Commons Zero (CC0) license. The model and code are completely free to use.

Other Language Examples

C++, C#, Crystal, Go, Java, JavaScript, Kotlin, Python, Ruby, Swift, TypeScript