Scala Parse String Class and Compile in Run-Time

Question

I want to implement a function in scala that can parse string of a source code (a class object) and compile it to an object in the run time.

For example, the function is what I have tried so far. My goal is that run it compiled in run-time environment, I can use it constructor or its function. This code has run-time error but I don't understand the how to fix the reflect class error. Thanks!

object test {
        def main(args: Array[String]): Unit = {
            val m = universe.runtimeMirror(getClass.getClassLoader)
            val tb = m.mkToolBox()
            val clazz = tb.compile(tb.parse("class insideclass {\n    val model_field = 5\n   def insideclass(model: Int) = {\n        val model_field = model \n    } \n\n    def test() : Int = {\n        model_field\n    }\n\n}\nscala.reflect.classTag[insideclass].runtimeClass"))().asInstanceOf[Class[_]]
            val classinside = universe.typeOf[Class[_]].typeSymbol.asClass
            val ctor = universe.typeOf[Class[_]].declaration(universe.nme.CONSTRUCTOR).asMethod
            val cm=m.reflectClass(classinside)
            val ctorm=cm.reflectConstructor(ctor)
            println(ctorm(10).test())
        }
    }

qihqi · Accepted Answer · 2016-11-10 23:32:18Z

1

The problem is that the outside compiler does not know that "insideclass" exists as a class definition. One solution is to make inside class extend some other class that is know to both inside and outside compiler, for example Function[Int, Int]. You will need to rename your "test" method to "apply" in this case.

val clazz = tb.compile(tb.parse("class PersonData(x:Int) extends  Function[Int, Int] {\n val allen = x.toInt\n\n override def apply(x:Int):Int = allen}\n scala.reflect.classTag[PersonData].runtimeClass"))().asInstanceOf[Class[_]]

val ctor = clazz.getDeclaredConstructors()(0)

val instance = ctor.newInstance(new Integer(1))
// this cast can succeed because the outside knows what is Function[Int, Int]
println(instance.asInstanceOf[Function[Int, Int]].apply(1))

answered Nov 10, 2016 at 23:32

qihqi

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