Dump object into file | Restore object from file later

[Skagen]

So I've messed around with XML and boost:serialization (which seems to be gone in the latest version btw) and God knows what.

I've spent so long trying to figure out this that I have decided that I really just need to ask someone. How can I do this? I have a class, like this:

#include <vector>
#include "Map.h"
#include "NPC.h"

using std::vector;

class Database
{

public:
vector<Map> maps;
vector<NPC> npcs;

Database()
{

// Populate the vectors and do initial stuff

}

};

Then elsewhere I do:

Database database;

// Let the game play for a while
do_stuff();
do_more_stuff();

// The database's members have now changed, time to save it into a file.
// This is where I have no idea what to do. 

And additionally I need to be able to load this into an object again. SOmething like this?

Database database;
// magic function to make the new object equal to the one saved from earlier 

[ModShop]

Well, you need to put all of the objects data members into the file in such a way that they can be accurately reloaded. Here's a simple method:

void save(const Object& obj)
{
    ofstream file("save.txt");

    file << ":x:" << obj.x << endl;
    file << ":y:" << obj.y << endl;
    file << ":end:" << endl;
}

void load(Object& obj)
{
    int tx, ty;
    ifstream file;
    string line;

    file.open("save.txt");

    while (file.good())
    {
        getline(file, line, ':');


        if (line=="x")
        file >> tx;
        if (line=="y")
        file >> ty;

        if (line=="end")
        {
            obj.init(tx, ty);
            break;
        }
    }
}

That's probably not the most efficient way for storing object data, but it works.

[Skagen]

Thanks you so much! But where do I put this code? Inside the class or elsewhere? Also, do I need to modify it to fit my class or is it plug'n'play?

[ModShop]

It will obviously need to be modified to save all your classes members. You will probably want to make it a global function, so all instances of your class can be saved at once, rather than one at a time (if it were a member function). Also, I would suggest that you add error checking to these functions. (file.good(), file.is_open(), etc)

[Skagen]

So here:
file << ":x:" << obj.x << endl;

I change this to real attributes and copy?

Also, the class has some vector members, is that possible?

[ModShop]

To your first question, yes. To your second, kindof. You will need to find a way to store all the elements of the vector, and then reload them. This can be done in a way similar to the first method I gave you.

[Skagen]

Perhaps with several files? Into a folder?

[ModShop]

Noooo, you would just implement a way of storing the vectors elements into the same file.

Try adding this into the loop that parses the file:

if (line=="intvec")
{
    while (true)
    {
        getline(file, line, ':');
 
        if (line=="element")
        {
            file >> tempInmt;
            vectorOfInts.push_back(tempInt);
        }
        if (line=="end")
        break;
    }
}