根据实例类

Question

是否可以根据扩展类将特征中定义的方法限制为某种类型？例如：

trait Score extends Ordered[Score] {

    val reducedValue: Float // must be implemented by extending classes

    def compare (that: Score): Int = this.reducedValue.compare(that.reducedValue)
}

case class MarksScore (set: Boolean) extends Score {

    val reducedValue = if (this.set) 1.0f else 0.0f
}

case class RankingScore (rank: Float) extends Score {

    val reducedValue = this.rank
}

这样MarksScore(true)与RankingScore(5)相当，这很好，但没有意义。所以我想将compare限制为相应类的对象，而不是Score的所有实现者。

Answer 1

关于这一点感觉并不正确，但它实现了我的要求：

trait Score[T <: Score[T]] extends Ordered[T] {

    val reducedValue: Float

    def compare (that: T): Int = this.reducedValue.compare(that.reducedValue)
}


case class MarksScore (set: Boolean) extends Score[MarksScore] {

    val reducedValue = if (this.set) 1.0f else 0.0f
}


case class RankingScore (rank: Float) extends Score[RankingScore] {

    val reducedValue = this.rank
}