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

i current project struggle understand went wrong in program. believe problem constructor. when call member function behaves haven't initialized class members.

here 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 single entry list     void insertbankdata(std::string filename); // populate list data file     void deletebankentry(std::string key); // delete single entry     void findbankentry(std::string key) const;  // find , display 1 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 file     void outputhashstatistic() const; // print hash stats private:     hashlist* hashlist;     tree* tree;     int count; // number of records     int hashsize; }; 

here 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 trying call:

void banklist::insertbankentry(string account, string level, string lname, string fname, float value)  // add single entry list {     bankcustomer* customer = new bankcustomer(account, level, lname, fname, value);     hashlist->insert(customer);     tree->insert(customer);     count++; } 

however, work if place code in 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!

in constructors hiding member variables (by declaring variables same name members) hence member variables remain un-initialized

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

just use

hashlist = new hashlist(); tree = new tree(); 

inside constructors.