Linked List class, how do I access the data of a nested node struct?

Question

I'm trying to write this Linked List class for my assignment and I'm trying to write a "for_each" function in the class that gives the user read-only access to the data in each node. However when I try to access the data in the nodes I get an error saying, "EXC_BAD_ACCESS(code=1, address=0x0)" How can I get access to my data without leaking memory? I assume that is what the error is referring to.

#ifndef LINKEDLIST_H
#define LINKEDLIST_H

#include <iostream>
#include <memory>

//template<typename T>
class LinkedList
{
private:

    struct Node
    {
        int data;
        std::shared_ptr<Node> next;

        Node(int d, std::shared_ptr<Node> n)
        :data(d)
        ,next(n)
        {}
        Node()
        {};
    };

    std::shared_ptr<Node> head;
    std::shared_ptr<Node> temp;
    std::shared_ptr<Node> current;

public:

    LinkedList()
       :head()
    {}

    LinkedList(LinkedList& other)
       :head(Clone(other.head))
    {}

    std::shared_ptr<Node> getStart()
    {
        return head;
    }

    void InsertAt(int value, std::shared_ptr<Node> &n)
    {
        n->next = std::make_shared<Node>(value, n->next);

    }

    void Insertion(int value)
    {
        Insertion(value, head);
    }

    void Insertion(int value, std::shared_ptr<Node> &n)
    {
        if (!n)
        {
            InsertAt(value, n);
            return;
        }

        if (value < n->data)
            Insertion(value, n->next);
        else
            InsertAt(value, n);
    }

    void Remove(int value)
    {
        Remove(value, head);
    }

    void Remove(int value, std::shared_ptr<Node>& n)
    {
        if (!n) return;
        if (n->data == value)
        {
            n = n->next;
            Remove(value, n);
        }
        else
        {
            Remove(value, n->next);
        }
    }

    void for_each(std::shared_ptr<Node> n)
    {
        if(!n) return;

        std::cout<<current->Node::data;  <---- //Here it keeps telling me I have bad_access
        for_each(current->next);               //"EXC_BAD_ACCESS(code=1, address=0x0)

    }

    std::shared_ptr<Node> Clone(std::shared_ptr<Node> n) const
    {
        if(!n) return nullptr;
        return std::make_shared<Node>(n->data, Clone(n->next));
    }

    LinkedList& operator = (const LinkedList& list)
    {
        this->Clone(list.head);
        return *this;
    }
};

#endif

WhozCraig · Accepted Answer · 2013-10-19 01:34:02Z

1

Not sure why you're using current in your for_each contract, In fact, I see no reason for current in any of this code, and sometimes, recursion isn't the solution:

void for_each(std::shared_ptr<Node> n)
{
    if(!n) return;

    std::cout<<current->Node::data;  <---- this is never set to anything
    for_each(current->next);
}

Try this:

void for_each(std::shared_ptr<Node> n)
{
    while(n)
    {
        std::cout << n->data << ' ';
        n = n->next;
    }
}

edited Oct 19, 2013 at 1:34

answered Oct 19, 2013 at 1:28

WhozCraig

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