overriding asType on String by Groovy

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このコードが使われている記事

• Groovyで既存クラスのasTypeをOverrideする

overrideAsType.groovy

enum Suit {
  S('♤♠'), H('♡♥'), D('♢♦'), C('♧♣'),
  def mark
  Suit(mark){ this.mark = mark }
}

enum Rank {
  R2, R3, R4, R5, R6, R7, R8, R9, R10, RJ, RQ, RK, RA
  def rank(){ this.name().substring(1) }
}

class Card {
  Suit s
  Rank r
  String toString() {
    switch(s) {
      case [Suit.H, Suit.D] : return "${s.mark[0]}${r.rank()}"
      case [Suit.S, Suit.C] : return "${s.mark[1]}${r.rank()}"
    }
  }
}

String.metaClass.define {
  oldAsType = String.metaClass.getMetaMethod("asType", [Class] as Class[])
  asType = { Class c ->
    if (c == Card)
      new Card(s:delegate[0] as Suit, r:'R'+delegate[1..-1] as Rank)
    else
      oldAsType.invoke(delegate, c)
  }
}

assert ('C5' as Card) instanceof Card
assert ('C5' as Card).toString() == '♣5'
assert ('D10' as Card).toString() == '♢10'