Thread: Self referential class || Stroring an address of a class

Can we use a self referential class in C++? If yes what is the difference between self referencing in C and in C++

Is there any problems in storing the address of classes?

PS: I wrote a program using the concept in C++ but it isn't working. Reply asap

Fine I meant the address of the objects!

So if you mean "can an object store its own address", then the answer is yes. In fact, you cannot stop an object from storing its own address, as that is what "this" represents.

I want to make the objects linked

Okay. There's not really anything stopping you from doing so. Use the & operator to get an address from an object.

If there's some error with the code you've written, you can get actual advice and hints if you tell us (a) what you did (i.e. show us what you've written) and (b) what errors you are getting.

Here is the code. The program is very simple, a book shop - in admin mode we need add books as in client mode we can subscribe them. I want to do this program using dynamic memory allocation not array of objects.

Code:

/*Sarath*/

#include<iostream.h>
#include<conio.h>

class bookshop;

bookshop *start,*temp,*ptr;

class bookshop        //self referential class to define a bookshop
{

	char title[20];           //to store book title
	char author[20];          //to store author name
	float price;              //price of the book
	int copies;               //no: of copies
	public:
	class bookshop *next;     //to point to node of same class

	public:

	bookshop(bookshop *);
	void admin();              //to enter new stock
	void client();             //to search and purchase
	void display();            //to display book details

};

bookshop::bookshop(bookshop *temp)    //parametrised constructor
{                                     //to insert new node
	if(start==NULL)
	{
		start=temp;
		start->next=NULL;
	}
	else
	{

		ptr=start;
		while(ptr->next!=NULL)
			ptr=ptr->next;
		ptr->next=temp;
		temp->next=NULL;
	}
}

void main()
{

	int choice;
	start=NULL;
	clrscr();

	do
	{
		cout<<"\n\n\tBook Shop\n";
		cout<<"\n\t1. Admin\n\t2. Client\n\t3. Quit";
		cout<<"\n\n\tChoice: ";
		cin>>choice;

		bookshop *temp=new bookshop(temp);
		switch(choice)
		{

			case 1:
				temp->admin();
				break;
			case 2:
				temp->client();
				delete temp;     //to delete last node
				break;
			case 3:
				cout<<"\n\tPress any key to quit..";
				break;
			default:
				cout<<"\nInvalid choice!\n";

		}

	}while(choice!=3);

	getch();

}

void bookshop::admin()
{
	cout<<"\n\tBook title: ";
	cin>>title;
	cout<<"\n\tAuthor: ";
	cin>>author;
	cout<<"\n\tPrice: ";
	cin>>price;
	cout<<"\n\tNo of copiess: ";
	cin>>copies;
	display();
}

void bookshop::client()
{
	start->display();
	int flag=0;
	cout<<"\n\tTitle?:";
	cin>>title;
	cout<<start;
	ptr=start;

	while(ptr->next!=NULL)
	{

		if(ptr->title==title)
		{

			ptr->display();
			flag=1;
			break;

		}
		ptr=ptr->next;
	}

	if(flag==0)
		cout<<"\n\n\t"<<title<<" is not available!";

}

void bookshop::display()
{

	cout<<"\n\n\t"<<title<<" is available";
	cout<<"\n\tAuthor: "<<author;
	cout<<"\n\tPrice: "<<price;
	ptr=start;
	while(ptr!=NULL)   {
	cout<<" "<<ptr->title;          ptr=ptr->next;}

}

Whats wrong in main? Linking is working well[I have checked by printing the addresses of the objects] But the problem is that I cant access the members using the object pointer.

No syntax errors. But when I print the values using "start->title" I am getting smileys and all

For a minute there I thought I was in the C forum section..

1) This isn't C++, it's "C with classes"
2) Replace your compiler with a standard-compliant one. iostream.h is pre-standard and deprecated.
3) Why are you rolling your own linked list? Use std::list
4) Why does each bookshop only hold one book? I suggest a single class bookshop which can hold several class book, in for example an std::list or vector
5) main is leaking memory. Look up RAII and smart pointers.
6) "bookshop *temp=new bookshop(temp);" temp is uninitialized when passed to bookshop()

I am not an expert in C/C++. Thats the answer for all the 'whys'. And thanks for the suggestions

@ sarath :
I I just read thcode. I think ur problem is that u can't search for a particular book. The mistake is , u have used == operator to compare strings.. Instead u should use strcmp()..

@others :
try to understand what is the problem he is facing.. And make him clarify it rather than confusing him with much complex things.