Question

I have an interface Class object provided as a method parameter, and I also have a Object instance of the object being casted.

Task: To cast the object as if I would do the interface = object thing but manually using Class.cast() method.

And the star of the show:

def readObject(type, path) {
        Object obj
        // Prevent playing with NPE
        if (groovyClassLoader == null)
            groovyClassLoader = new GroovyClassLoader(getClass().getClassLoader())

        // The final quest begins
        try {
            Class groovyClass = groovyClassLoader.parseClass(new File(path))

// at this point: type ins an instance of Class which is an interface
// to which I need to assign the obj instance

// groovyClass is an instance of Class 
// out of which I need to get object and eventually cast it to type
// so something like:
//            groovyClass = groovyClass.cast(type)
//            obj = groovyClass.newInstance()
// or
//            obj = groovyClass.newInstance()
//            obj = groovyClass.cast(type)



            obj = groovyClass.newInstance()
            obj = type.cast(obj)

        } catch (ex){
            //TODO:IO and obj creation exception should be logged
            ex.printStackTrace()
        }
        return obj
    }

This is a mighty warior quest for survival with mage casting and I’m starting to feal that my mission is out of mighty land possibilities XD

Answer 1

You cannot create an instance of an interface. You must first define a class that implements the interface and then create an instance of that class. You can then pass this object as an argument to any method that accepts a parameter of the interface type.