Storing Objects in an Array

Hi,

Thanks for the help earlier on on another problem, now for a new one....

I wish to store objects (I think I actually mean object pointers, but I am sure you will tell me if I'm wrong) in an array. Through my searching people seem to suggest the following:


MyClass *test[10];
test[0] = new MyClass();
test[1] = new MyClass();

// etc....

test[0]->add_info("foo");
test[1]->add_info("bar");

// etc....

cout << "Info for test0: " << test[0]->get_info();
cout << "Info for test1: " << test[1]->get_info();



Now, I have tried this and essentially each time I do an add_info call, it replaces my existing data - regardless of me choosing a different array index. (So, a test[1] add_info call, replaces the data in test[0] as well as test[1])

I'm sure that I am doing something utterly stupid here, would anyone mind telling me where I am going wrong??

What is the definition of the MyClass class? You might want to post the smallest and simplest compilable program that demonstrates the problem.

The MyClass header file is as follows:

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

class MyClass
{
public:

void add_info(std::string);
std::string get_info();

};


the implementation file:


#include "stdafx.h"
#include <iostream>
#include "ProductInfo.h"
#include <string.h>
using namespace std;

std::string info;

void MyClass::add_info(std::string input_info) {
info = input_info
}


std::string MyClass::get_info() {
return info;
}




So its basically that stuff above..

The original code posted being from the driver program.

You probably don't really need to use pointers.

Code:

---

MyClass test[10]; // Declare 10 MyClass objects, each constructed with the default constructor.

test[0].add_info("foo"); 
test[1].add_info("bar");

---

You have a global std::string info;
Declare it in MyClass.

No Dice.

The same problem occurs.

the call's:

cout << test[1].get_info() << "\n";
cout << test[0].get_info() << "\n";

both return "bar"

In response to your other reply: Declare it in the implementation or the header?? (it already exists in the implementation)

I declared them private in the header, and it seemed to work. I'll test it with the rest and get back to you

You can remove the global one in the implementation file to avoid confusion.

Thanks for the explanation why Lindley. And thanks for identifying the problem JohnW@Wessex.

Problem sorted. I officially love this forum.

I also officially appologise for my sucky ability when it comes to c++ and OOP theory in general, and for the numerous other threads that will surely appear over the next few weeks!!

Dave.

Quote:

---

Originally Posted by skycrazy123

I declared them private in the header, and it seemed to work.

---

Yes, that is a correct fix since you want info to a non-static member variable so that each MyClass has its own copy.

By the way, you should #include <string>, not <string.h> since you are using std::string instead of the string functions inherited from C (in which case you should #include <cstring>). Also, you should remove the using directive at file scope (using namespace std; ) from the header file. To be const-correct, your get_info() member function should be declared const.

Quote:

---

Originally Posted by laserlight

you should #include <string>, not <string.h> since you are using std::string instead of the string functions inherited from C (in which case you should #include <cstring>). Also, you should remove the using directive at file scope (using namespace std; ) from the header file.

---

I know, I just hadnt got around to updating the files yet (but thanks for reminding me)

Dave.