CODEWITHSUNDEEP
c++objectserialization
pittuzzo
pittuzzo

Reputation: 491

c++ serialization of a structure

While compiling this simple code:

#include <fstream>
#include <iostream>
#include <string.h>
using namespace std;

class Example
{
    public:
        char  charo;
        int   into;
};

int main()
{
    Example one,two;

    one.charo = 'X'; one.into = 2;

    //WRITING
    ofstream file;
    file.open("my.prx", ios_base::binary);
    if(file.good()) file.write((char*)&one, sizeof(Example));
    else cout << "ERROR WHILE OPENING FILE" << endl;
    file.close();

    //READING
    file.open("my.prx", ios_base::binary);
    if(file.good())
    file.read((char*)&two, sizeof(Example));
    else cout << "ERROR WHILE OPENING FILE" << endl;
    file.close();

    //PRINTING
    cout << "CHAR: " << two.charo << endl;
    cout << "INT: " << two.into << endl;

}

I get this error message:

g++ -o test1 main.c main.c: In function ‘int main()’: main.c:43:7: error: ‘std::ofstream’ has no member named ‘read’
file.read((char*)&two, sizeof(Example));

How can I solve it? My next step will be to make a more complicated object to save:

Class Memory{
    t_monitor monitors[MAX_MONITORS];
    t_status status[MAX_STATUS]; 
    t_observer observers[MAX_OBSERVERS];
    Var * first_var;
    int tot_observers;
    int tot_status;
    int tot_monitors;   
};

As you can see there is also a list...

Upvotes: 3

Views: 363

Answers (3)

Vinay Shukla
Vinay Shukla

Reputation: 1844

Use ifstream to read ostream is used for output.

You can do something like this 

std::ifstream fileRead( "my.prx",std::ifstream::binary );
if(fileRead)
fileRead.read((char*)&two, sizeof(Example));
else cout << "ERROR WHILE OPENING FILE" << endl;
fileRead.close();

Upvotes: 1

Erik Aronesty
Erik Aronesty

Reputation: 12897

An [ofstream][1] is output only. One readable way is to use the variables ofstream ofile and ifstream ifile. This way the usage is clear from the declaration and the name. If the code grows, this might be helpful.

Another way would be to use the dual-use fstream, but this can make certain operations ambiguous.

Of course, these days, you're probably better off using some sort of serialization library. First, preferring the one that your company or group already uses, and then, if that one is inadequate, picking a modern lib like Boost or, my fave, Cereal.

Upvotes: 1

Amit
Amit

Reputation: 46323

ofstream is an output file stream. It's used for output, and can't "read".

Use fstream instead.

Upvotes: 2

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