Access outer class function from Object of Inner Class

Question

I know there are similar question put up related to this issue, but however, I wasn't able to resolve my issue. I've tried to simplify my problem to the following code -

class Outer
{
    Outer()
    {}

    class Inner
    {
        Inner()
        {}
    }

    void func()
    {
        System.out.println("Outer");
    }
}

public class Nested
{
    public static void main(String args[])
    {
        Outer oo = new Outer();
        Outer.Inner ii = oo.new Inner();

//          ii.func(); I know this won't work


    }
}

Can I call outer class function "func()" from object of inner class "ii"..?? If yes, how?

why do you want to call from inner class when you could clearly do it from outer? — SMA, Apr 25 '15 at 10:23
Duplicate : http://stackoverflow.com/questions/1816458/getting-hold-of-the-outer-class-object-from-the-inner-class-object — Ankur Anand, Apr 25 '15 at 10:38

score 4 · Accepted Answer · answered Apr 25 '15 at 10:25

4

Short answer: the reference to Outer.this is private in Inner so you cannot access the reference to the Outer instance from an instance of the Inner.

You can export this reference thus:

class Outer {
    Outer() {
    }

    class Inner {
        Inner() {
        }

        public Outer getOuter() {
            return Outer.this;
        }
    }

    void func() {
        System.out.println("Outer");
    }
}

Then you can simply do:

ii.getOuter().func();

answered Apr 25 '15 at 10:25

Boris the Spider

59,842
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Was just about to write exactly the same answer (even with the same method name) – Rohit Jain Apr 25 '15 at 10:26
@BoristheSpider seems like all great mind thinks same function name : Jon Skeet here same question http://stackoverflow.com/questions/1816458/getting-hold-of-the-outer-class-object-from-the-inner-class-object – Ankur Anand Apr 25 '15 at 10:41
@user3554962 rather than commenting with thank-yous, please consider [accepting an answer](http://meta.stackexchange.com/questions/5234/how-does-accepting-an-answer-work) if you question was answered. – Boris the Spider Apr 26 '15 at 19:33

score 1 · Answer 2 · answered Apr 25 '15 at 10:24

1

Use Outer.this.func() from the inner class. Do note that you can only do this from the inner class, not from outside.

answered Apr 25 '15 at 10:24

Distjubo

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`Outer.this` is `private` in `Inner`. You cannot access it like that. – Boris the Spider Apr 25 '15 at 10:26
Lol thats exactly what I mean – Distjubo Apr 25 '15 at 10:27
Well then it's not very helpful to the use case of the OP is it? I.E. it doesn't actually answer the question. – Boris the Spider Apr 25 '15 at 10:27
It answers the question. Read the last line of the question carefully. – Distjubo Apr 25 '15 at 10:29
The OP wants to access the method `func` on `Outer` from an instance of `Inner` in _another class_ - `Nested`. This does not answer the question, it answers a different question. – Boris the Spider Apr 25 '15 at 10:30
@BoristheSpider Read this quote: "Can I call outer class function "func()" from object of inner class "ii"..??" The answer is, as mentioned, no. – Distjubo Apr 25 '15 at 10:35
Yes, _from an object in inner class_. I have an `Inner ii`, how do I call `func()` using your method?? – Boris the Spider Apr 25 '15 at 10:40
There is no way to do so without providing new methods in ii. That is EXACTLY what I tried to tell you. – Distjubo Apr 27 '15 at 16:25
Is it? I don't see any mention of "new" or "method" in your answer. You answer just says _Use `Outer.this.func()` from the inner class._ I still insist that this answer doesn't even come close to answering the question. Maybe the comments clarify things a little, but the answer it still useless. – Boris the Spider Apr 27 '15 at 16:30
If you are not happy with my answer, feel free to EDIT it. – Distjubo Apr 28 '15 at 13:38
Also, read it again, what would you do if I say that you can only use the scope from the inner class? – Distjubo Apr 28 '15 at 13:45

score 1 · Answer 3 · answered Apr 25 '15 at 10:28

class Outer {
   Outer() {}
   class Inner {
     Inner() {}

     void callFunc() {
       Outer.this.func();
     }
  }

  void func() {
     System.out.println("Nested");
  }
}

public class Nested {
 public static void main(String args[]) {
   Outer.Inner ii = new Outer().new Inner();
   ii.callFunc();

 // ii.func(); I know this won't work
 }
}

score 1 · Answer 4 · answered Apr 25 '15 at 10:31

This will work for you

package com;


class Outer
{
    Outer()
    {}

    class Inner
    {
        Inner()
        {}
        public Outer g(){
            return Outer.this;}
    }

    void func()
    {
        System.out.println("Outer");
    }
}

public class Test1
{
    public static void main(String args[])
    {
        Outer oo = new Outer();
        Outer.Inner ii = oo.new Inner();


         ii.g().func(); 


    }
}

Access outer class function from Object of Inner Class

4 Answers4