scala - 如何以编程方式编译和运行 Scala 代码

Question

我有以下代码，我想即时编译并运行它。

object HelloWorld {
  def main(args: Array[String]): Unit = {
    println("Hello, world!")
  }
}

到目前为止，我已经尝试过类似下面的方法:

import scala.reflect.runtime.currentMirror
import scala.tools.reflect.ToolBox

object MainScala {
  def main(args: Array[String]): Unit = {
    val toolbox = currentMirror.mkToolBox()
    val source =
      """
        |object HelloWorld {
        |  def main(args: Array[String]): Unit = {
        |    println("Hello, world!")
        |  }
        |}
        |""".stripMargin
    val tree = toolbox.parse(source)
    val binary = toolbox.compile(tree)
    var c = binary.getClass
    val m = c.getMethod("main", classOf[Array[String]])
    val params = Array("Apple", "Banana", "Orange")
    m.invoke(null, null)
  }
}

在 toolbox.compile(tree) 之后，我无法获得编译代码的 Class 对象。

Answer 1

如果您查看 binary 的类型，您会看到它是 () => Any。因此，当您询问 .getClass 时，您实际上得到了 Function1 的子类，它没有 .main。

工具箱不应该这样使用。

https://github.com/scala/scala/blob/2.13.x/src/compiler/scala/tools/reflect/ToolBox.scala#L120-L129

https://docs.scala-lang.org/overviews/reflection/symbols-trees-types.html#tree-creation-via-parse-on-toolboxes

尝试

val source =
  """
    |object HelloWorld {
    |  def main(args: Array[String]): Unit = {
    |    println("Hello, world!")
    |  }
    |}
    |
    |HelloWorld.main(Array())
    |""".stripMargin
val tree = toolbox.parse(source)
val binary = toolbox.compile(tree)
binary() // Hello, world!

或

val params = """Array("Apple", "Banana", "Orange")"""
val source =
  s"""
    |object HelloWorld {
    |  def main(args: Array[String]): Unit = {
    |    println(args.toList)
    |  }
    |}
    |
    |HelloWorld.main($params)
    |""".stripMargin
val tree = toolbox.parse(source)
val binary = toolbox.compile(tree)
binary() // List(Apple, Banana, Orange)

或

import scala.reflect.runtime.universe._
val params = q"""Array("Apple", "Banana", "Orange")"""
val tree =
  q"""
    object HelloWorld {
      def main(args: Array[String]): Unit = {
        println(args.toList)
      }
    }

    HelloWorld.main($params)
    """
val binary = toolbox.compile(tree)
binary() // List(Apple, Banana, Orange)

或

val params = """Array("Apple", "Banana", "Orange")"""
val source =
  """
    |object HelloWorld {
    |  def main(args: Array[String]): Unit = {
    |    println(args.toList)
    |  }
    |}
    |""".stripMargin
val tree = toolbox.parse(source)
val symbol = toolbox.define(tree.asInstanceOf[ImplDef])
val params1 = toolbox.parse(params)
val tree1 = q"$symbol.main($params1)"
val binary = toolbox.compile(tree1)
binary() // List(Apple, Banana, Orange)