scala - 案例类的收缩宏

Question

我正在为我的案例类实现Shrink 实例。在我看来，宏可以完成这项工作。有人实施了吗？

Answer 1

是的，他们有！shapeless -contrib有一个Shapeless的实例TypeClass：Shrink

scala> import org.scalacheck._
import org.scalacheck._

scala> case class Foo(s: String, i: Int)
defined class Foo

scala> val unshrunk = Foo("This is a very long string", 1000)
unshrunk: Foo = Foo(This is a very long string,1000)

scala> implicitly[Shrink[Foo]].shrink(unshrunk) // boring default instance
res0: Stream[Foo] = Stream()

scala> import shapeless.contrib.scalacheck._
import shapeless.contrib.scalacheck._

scala> implicitly[Shrink[Foo]].shrink(unshrunk) // interesting instance
res1: Stream[Foo] = Stream(Foo(This is a ver,1000), ?)

这由宏支持，但仅限于 Shapeless 用于其Generic机器的宏。