根据实例 class 类型限制特征方法

Question

是否可以根据扩展 class 将特征中定义的方法限制为特定类型？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) 就相当于 RankingScore(5)，这很好，但毫无意义。所以我想将 compare 限制为各自 class 的对象，而不是 Score.

的所有实现者

Answer 1

有些地方感觉不太对，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
}

根据实例 class 类型限制特征方法

Type restricting trait methods depending on instance class

scala

types

traits