Functions which create objects.

Hi,

I am trying to do the following:

1) Call a function
2) Ask the user for the datamember values
3) Create the object
4) Return to main() a pointer to the object
5) Push that pointer into the std::list

But I'm having trouble.

Here is what I've made:

base.h:

Code:

---

#include <iostream>
#include <string>
using namespace std;

class Base
{
public:

        //Member Functions:
        Base * createABaseObject();//Create an object and return a pointer to it

private:

protected:

        //Data Members common to all objects (abstract base class):
        string _mystring;

};

---

base.cpp:

Code:

---

#pragma once

#include <iostream>
#include <string>
#include "base.h"

Base * Base::createABaseObject()
{
        //Build an object and return a pointer to the object.
        //Then within main(), the pointer can be pushed into the std:list

        cout << "You chose to create an object" << endl;

        string mystring;
        cout << "Value? " << endl;
        getline (cin, mystring);

        //create the object
        Base *ptr = new Aircraft(mystring);

        //return a pointer to main()
        return(ptr);
}

//constructor
Base::Base(string mystring)
{
        _mystring = mystring;
}

---

main.cpp:

Code:

---

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

int main()
{
        typedef list<Base *>BaseList;

        do{
                char choice;
                cout << "Choose one of the options below:" << endl;
                cout << "a) Enter a base class pointer into the list" << endl;
                cin >> choice;
                cin.ignore();

                switch(choice)
                {
                case 'a':
                        {
                                //Create an object and return a pointer to the object
                                createABaseObject();

                                //push the returned pointer onto the list
                                BaseList.push_back( ptr );

                                cout << "Object pushed onto list" << endl;
                                break;
                        }
                default:
                        {
                                cout << "You made an invalid choice" << endl;
                                break;
                        }
                }
        }
        while(true);

        system("pause");
}

---

This isn't compiling, and was hoping someone could comment on where I'm going wrong.

Any help is really appreciated.

Thanks

You need to do something like:

Code:

---

Base *ptrBase = createABaseObject();
BaseList.push_back(ptrBase);

---

IOW you are not taking what your own factory (createABaseObject()) is returning to you.. you are just discarding it...and leaking..

There's hardly anything which is right :(

Firstly, are you dealing with a class called Aircraft or a class called Base?

It also seems that createABaseObject is a member function of Base (or Aircraft). As such you'll first need a Base object to call this function on - as it is, you first need a Base to ask it to create other Bases - which doesn't seem to make much sense here to begin with.

Wont he need to declare a variable of BaseList type?

Code:

---

BaseList MyList;

---

Then use Mylist

Code:

---

Mylist.pushback(createABaseObject());

---

EDIT: oops, and like anon mentions, you'll need an instance of base to call createABaseObject, or not have the function as a member. You might be able to just do Base::createABaseObject(), but don't take my word for it.

Quote:

---

Originally Posted by Syneris

Wont he need to declare a variable of BaseList type?

Code:

---

BaseList MyList;

---

---

Yes

Quote:

---

You might be able to just do Base::createABaseObject(), but don't take my word for it.

---

Declare createABaseObject() as a static method and you can do Base::createABaseObject();