Bridge Pattern in Scala

1Problem.scala

// Adding new functionality via inheritance leads to combinatorial explanation

abstract class Serializer {
  def write(string: String): Unit
}

class CsvFileWriter extends FileWriter {
  def writeFile(file: java.io.File) = //...
}

class JsonFileWriter extends FileWriter {
  def writeFile(file: java.io.File) = //...
}

2PatternSolution.scala

// Separate out the concern that doesn't belong in the class hierarchy, thus creating a separate hierarchy

type Format = (String => String)

class FileWriter {
  def writeFile(file: java.io.File, format: Format): Unit = format(...)
}

class EncryptedFormat extends Format {
  def apply(str: String) = //...
}

class CSVFormat extends Format {
  def apply(str: String) = //...
}

val EncryptedCSV = new EncryptedFormat compose new CSVFormat

3Typeclass.scala

trait Format extends (String => String)

object Format {
  implicit object EncryptedFormat extends Format {
    def apply(str: String) = //...
  }
}

import Format._
class DiskWriter extends Writer {
  def writeFile(file: java.io.File)(implicit format: Format): Unit = format(...)
}

class DatabaseWriter extends Writer {
  def writeFile(file: java.io.File)(implicit format: Format): Unit = format(...)
}