Accessing field of outer class

Question

How do I access a field of an outer class, given a reference to an object of the inner class?

class Outer
{
    int field;

    class Inner
    {
        void method(Inner parameter)
        {
            // working on the current instance is easy :)
            field = 0;
            Outer.this.field = 1;

            // working on another instance is hard :(
            parameter.field = 2;              // does not compile
            parameter.Outer.this.field = 3;   // does not compile
            parameter.outer().field = 4;      // This works...
        }

        // ...but I really don't want to have to write this method!
        Outer outer()
        {
            return Outer.this;
        }
    }
}

I also tried Outer.parameter.field and many other variants. Is there a syntax that does what I want?

Answer 1

From outside the inner class, I believe that there's no way, given a reference to an inner class instance, to reference members of the outer class instance. From inside a non-static inner class, you can, of course, reference them using the Outer.this.* syntax.

Think of it this way: the inner class is actually a completely separate class. It has a compiler-generated field (usually named something weird like this$0). Within the inner class, the language allows you to reference that field using Outer.this; however, that syntactic sugar is not available outside the inner class itself. Neither is the compiler-generated field.

Answer 2

How about this solution:

class Outer
{
    int field;

    class Inner
    {
        final Outer outer = Outer.this;
        void method(Inner parameter)
        {
            // working on the current instance is easy :)
            field = 0;
            Outer.this.field = 1;

            // working on another instance:
            parameter.outer.field = 2; 
        }
    }
}