scala – 将String转换为可运行代码的方法有哪些？

发布时间：2020-12-16 09:07:52 所属栏目：安全来源：网络整理

导读：我找不到如何将String转换为可运行的代码,例如： val i = "new String('Yo')"// conversionprintln(i) 应该打印 Yo 转换后. 我在另一篇文章中找到了以下示例： import scala.tools.nsc.interpreter.ILoopimport java.io.StringReaderimport java.io.StringWr

我找不到如何将String转换为可运行的代码,例如：

val i = "new String('Yo')"
// conversion
println(i)

应该打印

Yo

转换后.

我在另一篇文章中找到了以下示例：

import scala.tools.nsc.interpreter.ILoop
import java.io.StringReader
import java.io.StringWriter
import java.io.PrintWriter
import java.io.BufferedReader
import scala.tools.nsc.Settings

object FuncRunner extends App {

  val line = "sin(2 * Pi * 400 * t)"

  val lines = """import scala.math._
    |var t = 1""".stripMargin

  val in = new StringReader(lines + "n" + line + "nval f = (t: Int) => " + line)
  val out = new StringWriter

  val settings = new Settings

  val looper = new ILoop(new BufferedReader(in),new PrintWriter(out))
  val res = looper process settings
  Console println s"[$res] $out"
}

链接：How to convert a string from a text input into a function in a Scala

但似乎scala.tools不再可用了,而且我是Scala的新手,所以我无法弄清楚如何更换它.
也许现在还有其他方法可以做到.

谢谢！

解决方法

您可以使用Quasiquotes(实验模块)简单地执行String中包含的代码.

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

// TO compile and run code we will use a ToolBox api.
val toolbox = currentMirror.mkToolBox()

// write your code starting with q  and put it inside double quotes.
// NOTE : you will have to use triple quotes if you have any double quotes usage in your code.
val code1 = q"""new String("hello")"""
//compile and run your code.
val result1 = toolbox.compile(code1)()

// another example
 val code2 = q"""
 case class A(name:String,age:Int){
    def f = (name,age)
 }
 val a = new A("Your Name",22)
 a.f
 """

 val result2 = toolbox.compile(code2)()

REPL中的输出：

// Exiting paste mode,now interpreting.

import scala.reflect.runtime.universe._
import scala.reflect.runtime.currentMirror
import scala.tools.reflect.ToolBox
toolbox: scala.tools.reflect.ToolBox[reflect.runtime.universe.type] = scala.tools.reflect.ToolBoxFactory$ToolBoxImpl@69b34f89
code1: reflect.runtime.universe.Tree = new String("hello")
result1: Any = hello
code2: reflect.runtime.universe.Tree =
{
  case class A extends scala.Product with scala.Serializable {
    <caseaccessor> <paramaccessor> val name: String = _;
    <caseaccessor> <paramaccessor> val age: Int = _;
    def <init>(name: String,age: Int) = {
      super.<init>();
      ()
    };
    def f = scala.Tuple2(name,age)
  };
  val a = new A("Your Name",22);
  a.f
}
result2: Any = (Your Name,22)

scala>

要了解有关Quasiquotes的更多信息：
http://docs.scala-lang.org/overviews/quasiquotes/setup.html

（编辑：李大同）

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