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，我已经尝试了如下方法：

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)
}
}

toolbox.compile(tree)之后，我无法获取编译代码的Class对象。

Answer 1

如果你看一下binary的类型，你会发现它是() => Any。所以当你问.getClass你实际上得到了一个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)