[英]Class type parameters in Scala.
I'm having difficulty writing something that should be quite straight-forward, but I can't seem to get the syntax right. 我写一些应该很直接的东西很难,但我似乎无法正确理解语法。
I have a class hierarchy for foods: 我有食物的类层次结构:
Food :> Vegetable :> Bamboo
And for animals: 而对于动物:
Animal :> Herbivore :> Panda
And I'm trying to define an eat method in Animal, so that Pandas can't eat Vegetables in general, only Bamboo. 而我正试图在动物中定义一种吃法,这样熊猫一般不能吃蔬菜,只能吃竹子。 At the moment, my code looks like this: 目前,我的代码如下所示:
class Food(val name : String)
class Vegetable(name: String) extends Food(name)
class Bamboo extends Vegetable("bamboo")
class Animal[F <: Food](val name : String) {
def eat[T <: F](f : T) = println(s"$name eats some yummy ${f.name}")
}
class Herbivore[F <: Vegetable](name :String) extends Animal[Vegetable](name)
class Panda extends Herbivore[Bamboo]("panda")
my trouble is, that when I create a Vegetable, the Panda can eat it: 我的麻烦是,当我创造一个蔬菜时,熊猫可以吃它:
(new Panda) eat (new Vegetable("potato"))
So something's going wrong :( 出了点问题:(
Any help would be very welcome :) 任何帮助将非常欢迎:)
You need to change: 你需要改变:
class Herbivore[F <: Vegetable](name :String) extends Animal[Vegetable](name)
to: 至:
class Herbivore[F <: Vegetable](name :String) extends Animal[F](name)
Otherwise you're throwing out the type information by not using F. 否则你不会使用F丢弃类型信息。
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