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scalareflectionstructural-typing

Supply Structural type in method type parameterization at runtime?

Follow-up to this SO question.

Suppose I have the code 

def bar(param: {def foo: Unit}*) = param.foreach(x => x.foo)

This function causes object param to invoke a method named foo

[EDIT]

I was wondering if the following is possible (with or without reflection)

  • param is fixed at compile time, the name of the function (in this case foo) is supplied at runtime
  • both param and the name of the function foo are supplied at runtime
  • param is fixed at compile time, the name of the function, the function parameters, values and return types are supplied at runtime.

I realize Structural typing already uses reflection. So my question is if Scala can take care of it or if I have explicitly use reflection in my code. I think the 3rd one requires reflection for which I can use the ASM library.

Solution

  • If I understand your question:

    1. At compile-time, the compiler checks that each param has indeed a method foo with the correct signature.
    2. At runtime, reflection is used underneath to call the method foo of each param

    So you don't need to use reflection yourself, but you should keep it mind that reflection will be used at runtime, and could potentially decrease performances.