CODEWITHSUNDEEP
c++
KurodaTsubasa
KurodaTsubasa

Reputation: 25

C++ Access violation reading location, class this pointer is NULL

I would like to get some help with my current project as I struggle to understand what exactly went wrong in my program. I believe the problem is with my constructor. When I call member function it behaves as I haven't initialized my class members.

Here is my class:

class BankList {
public:
    // constructor
    BankList();
    BankList(int size);
    bool isEmpty() const;
    int size() const;
    void insertBankEntry(std::string account, std::string level, std::string lName, std::string fName, float value); // add a single entry to the list
    void insertBankData(std::string fileName); // populate list data from the file
    void deleteBankEntry(std::string key); // delete a single entry
    void findBankEntry(std::string key) const;  // Find and display one element using key
    void checkBankEntry(std::string account);
    void printHashBankData() const; // List data in hash table sequence
    void printHashKeyBankData() const; // List data in key sequence (sorted)
    void printTreeBankData() const; // Print indented tree
    void writeBankData(); // Write data to a file
    void outputHashStatistic() const; // print hash stats
private:
    HashList* hashlist;
    Tree* tree;
    int count; // number of records
    int hashSize;
};

Here are my constructors:

BankList::BankList()
{
    HashList* hashlist = new HashList();
    Tree* tree = new Tree();
    count = 0;
    hashSize = 0;
}
BankList::BankList(int size)
{

  HashList* hashlist = new HashList(size);
  Tree* tree = new Tree();
  count = 0;
  hashSize = size;
}

The function I am trying to call:

void BankList::insertBankEntry(string account, string level, string lName, string fName, float value)  // add a single entry to the list
{
    BankCustomer* customer = new BankCustomer(account, level, lName, fName, value);
    hashlist->insert(customer);
    tree->Insert(customer);
    count++;
}

However, it does work if I place this code in my function.

if (!tree || !hashlist)
{
  tree = new Tree();
  hashlist = new HashList();
}

main:

int size = getSize();
BankList* list = new BankList(size);
list->insertBankEntry("123412341234", "Gold", "Jonhson", "Steve", 1234.45);

Thanks in advance!

Upvotes: 0

Views: 589

Answers (1)

vsoftco
vsoftco

Reputation: 56557

In the constructors you are hiding the member variables (by declaring variables with the same name as the members) hence your member variables remain un-initialized

HashList* hashlist = new HashList(); // hiding the member variable this->hashlist
Tree* tree = new Tree(); // hiding the member variable this->tree

Just use

hashlist = new HashList();
tree = new Tree();

inside the constructors.

Upvotes: 2

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