scala - 隐式转换不起作用

Question

为什么不应用以下隐式方法？如何实现自动将 X 实例转换为 Y 实例，同时在范围内具有隐式 Conversion[X,Y] .

trait Conversion[X, Y] {
  def apply(x: X): Y
}
implicit object Str2IntConversion extends Conversion[String, Int] {
  def apply(s: String): Int = s.size
}
implicit def convert[X, Y](x: X)(implicit c: Conversion[X, Y]): Y = c(x)

val s = "Hello"
val i1: Int = convert(s)
val i2: Int = s // type mismatch; found: String  required: Int

Answer 1

让你的转换扩展Function1，那么你就不再需要辅助方法了:

trait Conversion[X, Y] extends (X => Y) {
  def apply(x: X): Y
}

// unchanged
implicit object Str2IntConversion extends Conversion[String, Int] {
  def apply(s: String): Int = s.size
}

// removed convert

// unchanged
val s = "Hello"
val i1: Int = convert(s)
val i2: Int = s