c++ class to read ascii file and make actions - c++

Question

I wrote a little c++ class that read a ASCII files each line can have
4 element (int, string, int, float)
1000 I 100 10.0
or 3 (int, string, int)
1001 E 100
which means that if the string is an I the fourth element exist, not otherwise.
I am trying to write a class to insert rows.
The code asks the user to insert the object properties and then writes to file
I want to add a check
if the string is "I" then should ask to insert the float otherwise leave empty.
#include <iostream>
#include <fstream>
using namespace std;
void writing();
void deleting();
void searching();
class orderbook
{
string text;
private:
double Price = (double) NULL;
public:
int Timestamp = 0;
string Operation;
long int Id;
orderbook(){};
orderbook(const string& name)
{
ifstream infile;
infile.open(name);
if(!infile.good())
{
cout << "File is not open";
}
else
{
string line;
while(getline(infile,line))
text = text + line + '\n';
}
};
string contetns()
{
return text;
};
void SetPrice(double x = NULL)
{
Price = x;
}
float GetPrice()
{
return Price;
}
void insert(const string& name)
{
long int Id;
double Price;
float a;
orderbook ob;
cout << "Please enter Timestamp : ";
cin >> ob.Timestamp;
cout << "Please enter the Operation type: ";
cin >> ob.Operation;
cout << "Please enter Id : ";
cin >> ob.Id;
if (ob.Operation == 'I')
{
cout << "Pleae enter the Price of order: ";
cin >> a;
ob.SetPrice(a);
}
else{
ob.SetPrice()
}
ofstream myfile;
myfile.open(name, ios::app | ios::out);
myfile << ob.Timestamp << "\t";
myfile << ob.Operation << "\t";
myfile << ob.Id << "\t";
// if (ob.GetType().GetProperty("Price") != null )
// {
// myfile << ob.GetPrice() << endl;
// }
// else
// {
// myfile << endl;
// }
myfile.close();
}
void deleting()
{
string line, record;
cout << "Please Enter the name of record you want to delete: ";
cin >> record;
ifstream myfile;
ofstream temp;
myfile.open("record.txt");
temp.open("temp.txt");
while (getline(myfile, line))
{
if (line.substr(0, record.size()) != record)
temp << line << endl;
}
cout << "The record with the name " << record << " has been deleted if it exsisted" << endl;
myfile.close();
temp.close();
remove("record.txt");
rename("temp.txt", "record.txt");
}
};
int main()
{
string filename;
cout<<"Please enter the full name of the data file: ";
cin>>filename;
orderbook ob(filename);
cout << "content: " << endl << ob.contetns() << endl;
ob.insert(filename);
cout << "content: " << endl << ob.contetns() << endl;
ob.deleting();
cout << "content: " << endl << ob.contetns() << endl;
}
I get this error
class_student.cpp:64:20: error: invalid operands to binary expression
('string'
(aka 'basic_string, allocator >') and 'int') if (ob.Operation == 'I')