implicit 可用于变量 伴生对象 参数 方法
object Math {
trait NumberLike[T] {
def divide(x: T, y: Int): T
}
object NumberLikes {
implicit object NumberLikeDouble extends NumberLike[Double] {
def divide(x: Double, y: Int): Double = {
println("o-------------")
x / y
}
}
}
class Number extends NumberLike[Double] {
def divide(x: Double, y: Int): Double = {
println("t-------------")
123.0
}
}
implicit val test = new Number
}
object Statistics {
import Math.NumberLike
def mean[T](xs: Vector[T])(implicit ev: NumberLike[T]): T = {
println(ev.isInstanceOf[NumberLike[T]])
ev.divide(xs.reduce(ev.plus(_, _)), xs.size)
}
}
测试对于mean的隐含参数，伴生对象的优先级高于变量，还有貌似泛型的类型可以根据参数推断，所以可以省略
转载请注明原文地址: https://ju.6miu.com/read-668590.html
