Pass class as value and create Instance

Question

I have many classes of a common base trait. I have a function that needs to create a new instance of a instance of one of these classes, but which one is only known at runtime.

Is it possible to pass this class as a parameter and create an instance at runtime in Scala?

I'm not even sure that the answer would be the best approach but currently it's the only thing I can think of.

Answer 1

You could pass the value thus:

myFunc(classOf[myObj])

to the method with signature

def myFunc(clazz : AnyRef)={ ...

but this smells bad. You're either looking at implementing a factory pattern, or better still you could use polymorphism and simply do:

myObj.myFunc

since your functionality is predicated on what class is involved.

Answer 2

Same as in Java:

classOf[MyClass].newInstance // calls the constructor without parameters
classOf[MyClass].getConstructor(/* parameter types */).newInstance(/* parameters */)

See Javadoc for Class.

This will work in any Scala version. Scala 2.10 has new reflection libraries, which are aware of Scala concepts.