scala-immutable-builder-pattern

name	scala-immutable-builder-pattern
description	Implementing the Builder pattern idiomatically in Scala using case classes and the copy method for immutability.

In distributed systems, objects should be immutable to prevent concurrency issues. The traditional mutable Builder pattern in Java/Python should be adapted to an immutable Builder in Scala using case classes.

Python (Mutable):

class TokenizerBuilder:
    def __init__(self):
        self._tokenizers = []
        
    def add_tokenizer(self, tokenizer):
        self._tokenizers.append(tokenizer)
        return self

Scala (Immutable):

case class TokenizerBuilder(tokenizers: Seq[BaseTokenizer] = Seq.empty) {
  
  // Returns a new builder instance rather than mutating the current one
  def addTokenizer(tokenizer: BaseTokenizer): TokenizerBuilder = {
    this.copy(tokenizers = this.tokenizers :+ tokenizer)
  }

  def build(): UniversalTokenizer = {
    new UniversalTokenizer(tokenizers)
  }
}

// Companion object provides a clean entry point
object TokenizerBuilder {
  def apply(): TokenizerBuilder = new TokenizerBuilder()
}

This guarantees that the builder is thread-safe and can be safely passed across closures in a distributed data pipeline.