Writing from file to class - c++

Question

Making a project I have to write patient database and I have a problem. Looking through guids in iтternet I dont understand how to read from file to class and how to write class into file(I realized it using common input, it is better to rewrite it).
And I dont understand how to make base constructor for char, like with int
point()
{
x=y=z=0;
}
need like
Patient()
{
name="Mike";
surename="Smith";
adress="New York";
ilness="Cold"
card_number=1;
}
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int add();
int read();
string path = "base.txt";
class Patient
{
private:
char *name;
char *surename;
char *adress;
char *ilness;
int *card_number;
public:
void set()
{
cout << "Enter name:";
cin >> name;
cout << "Enter surename:";
cin >> surename;
cout << "Enter adress:";
cin >> adress;
cout << "Enter diagnosis:";
cin >> ilness;
cout << "Enter card number:";
cin >> *card_number;
}
void show()
{
cout << "Name:" << name << endl;
cout << "Surename:" << surename << endl;
cout << "Adress:" << adress << endl;
cout << "Cardnumber:" << card_number << endl;
cout << "Diagnosis:" << ilness << endl;
}
void print()
{
cout << name << surename << adress << ilness << card_number << endl;
}
Patient()
{
}
Patient(const char* s)
{
int length = 0;
while (s[length++] != ' ')
;
name = new char[length];
for (int i = 0; i < length; i++)
name[i] = s[i];
length = 0;
while (s[length++] != ' ')
;
surename = new char[length];
for (int i = 0; i < length; i++)
surename[i] = s[i];
length = 0;
while (s[length++] != ' ')
;
adress = new char[length];
for (int i = 0; i < length; i++)
adress[i] = s[i];
length = 0;
while (s[length++] != ' ')
;
ilness = new char[length];
for (int i = 0; i < length; i++)
ilness[i] = s[i];
length = 0;
while (s[length++] != '\n')
;
card_number = new int[length];
for (int i = 0; i < length; i++)
card_number[i] = s[i];
}
};
int main()
{
char a;
cout << "Choose the action:" << endl;
cout << "a. Add new patient" << endl;
cout << "b. Delete patient" << endl;
cout << "c. Find for card number" << endl;
cout << "d. Find for ilnesses" << endl;
cin >> a;
switch (a)
{
case 'a':
add();
break;
case 'b':
read();
break;
default:
cout << "error" << endl;
}
system("pause");
return 0;
}
int add()
{
fstream file;
file.open(path, fstream::out | fstream::in | ofstream::app);
if (!file.is_open())
{
cout << "Error" << endl;
}
else
{
string str;
cout << "Opend" << endl;
cout << "Enter name" << endl;
cin >> str;
file << str<<" ";
cout << "Enter surename" << endl;
cin >> str;
file << str << " ";
cout << "Enter adress" << endl;
cin >> str;
file << str << " ";
cout << "Enter ilness" << endl;
cin >> str;
file << str << " ";
cout << "Enter card number" << endl;
cin >> str;
file << str<<"\n";
cout << "Sucsesfully added\n";
}
file.close();
return 0;
}
int read()
{
fstream file;
file.open(path, fstream::out | fstream::in | ofstream::app);
if (!file.is_open())
{
cout << "Error" << endl;
}
else
{
cout << "Opend" << endl;
string str;
Patient first;
while (file.read((char*)&first,sizeof(Patient)))
{
first.print();
}
}
file.close();
return 0;
}
Database example
Mike Smith New_York Cold 1
Charles Williams London Flu 2
Henry Roberts York Coronovirus 3
Robert Garcia Sydney Cold 4
methods how to write from file to class and from class to file

Answer 1

If you want to serialise your data structures, it's best to use a library and data format, such as JSON.
Personally, I recommend nlohmann::json because of it's ease of use and flexibility.
Overloading the constructor and serialising data
Overloading your constructor is nothing other than overloading another method in C++.
If your class is Patient:
#include <string>
#include <nlohmann/json.hpp>
using nlohmann::json;
using std::string; // Don't use using namespace std;!
class Patient {
public:
Patient() = default;
explicit Patient(const string& name, const string& surname,
const string& addr, const string& illness):
m_name(name), m_surname(surname), m_address(addr), m_illness(illness) {}
explicit Patient(const json& data) { fromJson(data); }
virtual ~Patient() = default;
json toJson() const {
return {
{ "Name", m_name },
{ "Surname", m_surname },
{ "Address", m_address },
{ "Illness", m_illness }
};
}
void fromJson(const json& data) {
if (data.contains("Name") && data["Name"].is_string()) {
m_name = data["Name"].get<string>();
} // and so on
}
void dumpJson(const string& filePath) const {
ofstream out(path, std::ios::out);
// error checking
out << filePath;
}
private: // members
string m_name;
string m_surname;
string m_address;
string m_illness;
};
I haven't tested this code and won't guarantee it will work first try, but it should point you in the right direction. This code requires at least C++11.