TestTraitEx3.groovy

class Item {
    String name
    int price
}

trait Trader {
  // property
  int availableMoney = 0 
  private int tradesDone = 0

  // method
  def buy(Item item) {
    if (item.price <= availableMoney) {
      availableMoney -= item.price
      tradesDone += 1
      println "${getName()} bought ${item.name}"
    }
  }

  def sell(Item item) {
    
  }

  // abstract method
  abstract String getName()
}



class Merchant implements Trader {
  String name
  
  // 實做抽象方法
  String getName() {
    return this.name
  }
}

def bike = new Item(name: 'big red bike', price: 750)
def paul = new Merchant(name: 'paul')

paul.availableMoney = 2000
paul.buy(bike) // prints "paul bought big red bike"

println paul.availableMoney // 1250