Using Scala reflection to compile and load object - scala

Question

Given the following String:
"println(\"Hello\")"
It is possible to use reflection to evaluate the code, as follows.
object Eval {
def apply[A](string: String): A = {
val toolbox = currentMirror.mkToolBox()
val tree = toolbox.parse(string)
toolbox.eval(tree).asInstanceOf[A]
}
}
However, lets say that the string contains an object with a function definition, such as:
"""object MyObj { def getX="X"}"""
Is there a way to use Scala reflection to compile the string, load it and run the function? What I have tried to do has not worked, if anyone has some example code it is very appreciated.

Answer 1

It depends on how strictly you define the acceptable input string. Should the object always be called MyObj? Should the method always be called getX? Should it always be 1 method or can it be multiple?
For the more general case you could try to extract all method names from the AST and generate calls to each one. The following code will call every method (and returns the result of the last one) that takes 0 arguments and is not a constructor, in some object, not taking inheritance into account:
def eval(string: String): Any = {
val toolbox = currentMirror.mkToolBox()
val tree = toolbox.parse(string)
//oName is the name of the object
//defs is the list of all method definitions
val ModuleDef(_,oName,Template(_,_,defs)) = tree
//only generate calls for non-constructor, zero-arg methods
val defCalls = defs.collect{
case DefDef(_,name,_,params,_,_)
if name != termNames.CONSTRUCTOR && params.flatten.isEmpty => q"$oName.$name"
}
//put the method calls after the object definition
val block = tree :: defCalls
toolbox.eval(q"..$block")
}
And using it:
scala> eval("""object MyObj { def bar() = println("bar"); def foo(a: String) = println(a); def getX = "x" }""")
bar
res60: Any = x