How to access the outer class object from the inner class in c++

Question

I am trying to access the outer class variable cell[i][j] from the inner class method iterateForward.

I do not want to pass this of outer class to iterateForward as iterateForward(Matrix&) , since it will add a parameter to iterateForward.

Inner class Method:

Pos Matrix::DynamicCellIterator::iterateForward(){
                    ....................
         (Example)    outerRef.cell[i][j].isDynamic = true;          
                    .....................
                    }

Here is my class:

 class Matrix { 
       class DynamicCellIterator{
            Cell* currentCellPtr;
            Matrix& outerRef;  //This will be the key by which i'll get access of outer class variables
        public:
            DynamicCellIterator(Matrix&);
                Pos iterateForward();
        };
        Cell cell[9][9];
        DynamicCellIterator dynIte(*this); // I have a problem of initializing the outerRef variable.
        Error errmsg;
        bool  consistent;


    public:
        Matrix();
        Matrix(Matrix&);
            ................
    }


//Here I tried to initialize the outerRef.
    Matrix::DynamicCellIterator::DynamicCellIterator(Matrix& ref){
        this->currentCellPtr = NULL;
        this->outerRef = ref;
    }

How can I initialize outerRef?

Not sure what error you're getting, but I'd write it Matrix::DynamicCellIterator::DynamicCellIterator(Matrix& ref):outerRef(ref){ — Joachim Isaksson, Jan 28 '12 at 17:37
Possible duplicate of [Can inner classes access private variables?](http://stackoverflow.com/questions/486099/can-inner-classes-access-private-variables) — Jason C, Oct 31 '16 at 23:18

Mat · Accepted Answer · 2012-01-29T06:35:16.600

You need to initialize member references in the constructor's initialization list. And do the same for the dynIte member: initialize it in outer's constructor.

Something like this:

class Outer {
    class Inner {
        int stuff;
        Outer &outer;

        public:
            Inner(Outer &o): outer(o) {
                // Warning: outer is not fully constructed yet
                //          don't use it in here
                std::cout << "Inner: " << this << std::endl;
            };
    };

    int things;
    Inner inner;

    public:
        Outer(): inner(*this) {
                std::cout << "Outer: " << this << std::endl;
        }
};

score 3 · Answer 2 · answered Jan 28 '12 at 17:33

3

Have the constructor of the inner class accept a pointer to an object of the outer class and store it in a data member for later use. (This is essentially what Java does automatically under the hood, btw.)

answered Jan 28 '12 at 17:33

fredoverflow

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I tried this only. But i am getting error in this line. `DynamicCellIterator dynIte(*this);` – Muthu Ganapathy Nathan Jan 28 '12 at 17:42
@EAGER_STUDENT: You need to look up initialization lists. – Puppy Jan 28 '12 at 17:48
@DeadMG could you tell me `DynamicCellIterator dynIte(*this);` is invalid? Though I know `this` pointer will be used only in functions, I need to know, how logically `DynamicCellIterator dynIte(*this);` is invalid and how it is valid in initialization lists. – Muthu Ganapathy Nathan Jan 28 '12 at 17:59
Show us the constructor of `DynamicCellIterator`. – fredoverflow Jan 28 '12 at 19:26

How to access the outer class object from the inner class in c++

2 Answers2