Reading database from file c++ -

i'm trying read database file.

here save_base method:

void data_base::save_base() {     fstream file;      file.open("base.dat", ios::in | ios::out | ios::trunc);      if(file.good()==true) {         node *p = new node();         p=first;          while(p) {             file << p->content->connect() << ";" << "\n";             p=p->next;         }         file.close();     }else{     cout << "err - opening file." << endl;     } } 

connect method:

string product::connect() {      ostringstream do_string;     do_string << lp;     string new_lp = do_string.str();      ostringstream do_string1;     do_string1 << count;     string new_count = do_string1.str();      ostringstream do_string2;     do_string2 << prize;     string new_prize = do_string2.str();      ostringstream do_string3;     do_string3 << vat;     string new_vat = do_string3.str();      string connected = type + ";" + new_lp + ";" + name + ";" + new_count + ";" + unit + ";" + new_prize + ";" + new_vat;     return connected; } 

and read_base method:

void data_base::read_base() {     fstream file;      file.open("base.dat", ios::in);     if(file.good()==true)     {         char data_row[50];         int i=1;         while(!file.eof()) {             file.getline(data_row,100);          string data_content[50];         int j = 0;          char *buff;         buff = strtok (data_row,";");         while (buff != null)    {             data_content[j] = buff;             buff = strtok (null, ";");             j++;         }         string type = data_content[0];         int lp;         istringstream iss1(data_content[1]);         iss1 >> lp;         double count;         istringstream iss2(data_content[3]);         iss2 >> count;         double prize;         istringstream iss3(data_content[5]);         iss3 >> prize;         double vat;         istringstream iss4(data_content[5]);         iss4 >> vat;          // sprawdzamy typ obiektu zapisanego w danym wierszu pliku         if(type == "product")         {              product new_prod(lp, data_content[2], count, data_content[4], prize, vat);             product *new_product = new product(new_prod);             this->add(new_product);         }         i++;         }     file.close();     }else{         cout << "err opening file." << endl;     } } 

i'm adding products database , works fine. saving file works great. main problem when i'm trying read database file. reading database file works fine, @ end, application won't end itself. think there still buffers close. don't know or how close them.

honestly - have quite lot of problems going on in code, , i'd suggest main problem you're perhaps still wrestling encapsulation. code uses mix of c , c++ styles guaranteed make code hard read , maintain, , that's why you're here , people struggling give answer.

that said, problem looks in save you're calling "new node()" looks you'd saving ... nothing. shouldn't querying existing value within product? edit: ah - no, re-assign "p = first" now, see. happens node allocated on previous line?

you have potential stack-clobber when of lines exceed 50 bytes:

char data_row[50]; int i=1; while(!file.eof()) {     file.getline(data_row,100); 

if have use char arrays, habbit of using sizeof:

file.getline(data_row, sizeof(data_row)); 

it took me few moments figure out istringstreams - you're trying convert strings numbers? simpler , more efficient written as:

unsigned int lp = atoi(data_content[1].c_str()); or unsigned int lp = strtoul(data_content[1].c_str(), null, 10); 

your read_base function, part of database, knows waaaay data records. need encapsulate record population away read_base looks more like:

void data_base::read_base() {     fstream file("base.dat", ios::in);     if(file.good() == false) {         cout << "error opening file." << endl;         return;     }      for(size_t rowno = 0; !file.eof(); ++rowno) {         row* row = data_type::make_object_from_row(file);         if(row != nullptr)             this->add(row);         }     } } 

you may need "factory pattern" how implement data_row base type let this. in short, make product inherit data_type above works. data_type::make_object_from_row read first part of row , enumerate type can like:

data_type* data_type::make_object_row_row(istream& file) {     switch(get_type(file)) {         case data_type_product: return new product(file);         case data_type_person: return new person(file);         default:           clog << "invalid type in database: " << type << endl;           return nullptr;     } } 

(this 1 possible approach).