Cannot access struct in h file

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August 17th, 2007, 12:10 AM

mantai007

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Cannot access struct in h file

I created a node class and list class and declared the struct in the private of BookNode.. everytime i compile it says name undeclared..
i have declared a pointer to that class to access it and getter/setter methods too. but the function cant see the struct itself

Code:

BookNode.h

#include <stdlib.h>
#include <stdio.h>
using namespace std;

#ifndef BOOKNODE_H
#define BOOKNODE_H

class BookNode
{
private:

   struct Anode
   {
      String name;
      Anode *next;
      Anode()
      {
         next = NULL;
         name = NULL;
      }
   };

typedef Anode* NodePtr;

public:
   BookNode *bn;
   NodePtr aptr;
 
   BookNode();
   void setBookname(String name);
   String getName();
   NodePtr getNext();
}

#endif //BOOKNODE_H
--------------------------------------
BookNode.cpp

#include "BookNode.h"
#include "BookList.h"

BookNode::BookNode()
{
   bn = new BookNode;
   name = NULL;
   next = NULL;
}

String BookNode::getName()
{
   return bn->name;
}

void BookNode::setName(String newName)
{
   bn->name = newName;
}

NodePtr getNext()
{
   return *next;
}
---------------------------------------
BookList.h

#include <stdlib.h>
#include <stdio.h>
using namespace std;

#ifndef BOOKLIST_H
#define BOOKLIST_H

class BookList
{
private:
   int listSize;

public:

   NodePtr head, tail;
   BookList *bl;
   
   BookList();
   bool addBook(String name);
   bool deleteBook(NodePtr);
}; 
#endif //BOOKLIST_H
----------------------------------------------
BookList.cpp

#include "BookList.h"
#include "BookNode.h"

BookList::BookList()
{
   head = new Anode;
   current = head;
}

bool BookList::addBook(String name)
{
   ....
   return TRUE;
}

bool BookList::deleteBook(NodePtr)
{
   ....
   return TRUE;
}

August 17th, 2007, 08:41 AM

nattylife

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youve declared Anode as a private member of BookNode. but in BookList, you have:

c Code:

Original - c Code
BookList::BookList() { head = new Anode; current = head; }

 
BookList::BookList()
{
   head = new Anode;
   current = head;
}

BookList doesnt know anything about Anode. try defining Anode outside of the class in the header file, then declaring an Anode inside your BookNode.

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August 17th, 2007, 09:19 AM

mantai007

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i didnt know you can define something out of a class.. because i thought Anoed which is a struct unique to BookNode and should be inside BookNode class...

August 17th, 2007, 09:35 AM

nattylife

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it may be unique but its only unique to BookNode in this case. yet you are trying to create an instance of it in BookList. you would need to define it outside of the class so that BookList can use it also or try a different design.

August 17th, 2007, 09:46 AM

f'lar

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He could define it in the class, and use scope resolution to tell the compiler what he wants. ... but he still has to make it public rather than private.

Code:

class BookNode
{
public:
    struct Anode
    {
        String name;
        // ...
    };
    //...
};

class BookList
{
public:
    BookList()
    {
        BookNode::Anode head;
        head.name = "Some book";
    }
};

It seems like what he really wants, though, is to have booknode inherit from Anode or use templates such that he can define Anode generically as a node in a list and have Booknode define the payload for this particular use/application.

Comments on this post

nattylife agrees: didnt even think about that. good point.

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Last edited by f'lar : August 17th, 2007 at 09:52 AM.

August 17th, 2007, 09:55 AM

f'lar

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Looking more at his code, I think he'll have a real problem when he runs that and tries to create his first instance of a booknode. When the booknode contsructor is first called, if will take bn (a booknode pointer) and create a new instance, which will of course call the booknode constructor which will take it's own bn and create another instance... and on to ifinity, or when memory runs out.

August 17th, 2007, 10:22 AM

mantai007

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I was originally thinking of creating just 1 Header file to make it simpler...
but that means i have to include the BookList methods as well as the BookNode methods..
So there would need to be 2 classes inside the one header file...

August 17th, 2007, 10:51 AM

nattylife

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flar makes another good point. you will want to rethink your design for the BookNode class. you wont need to have a BookNode as a member of BookNode. BookList will be the one that needs to have those. BookNode only needs enough to create itself and initialize its members.

August 17th, 2007, 10:56 AM

mantai007

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I see.. i wasnt too sure about the design because.. i have to create a BookList & BookNode class.

and wasnt too sure where to put the BookNode struct.. in the list.cpp or the node.cpp

#10

August 17th, 2007, 12:16 PM

nattylife

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well, your BookList is a list of BookNodes.
while you have a Anode as a member of the BookNode class, do you really need that? couldnt you just have BookNode be the Anode like

c++ Code:

Original - c++ Code
class BookNode { private: String name; BookNodenext; public: BookNode(); void setBookname(String name); String getName(); BookNode getNext(); }

 
class BookNode
{
   private:
      String name;
      BookNode*next;
 
   public: 
      BookNode();
      void setBookname(String name);
      String getName();
      BookNode* getNext();
}

that way your BookNode is 1 node object by itself. it contains the name and a pointer to another BookNode. and then BookList can maintain the nodes.
EDIT: out of curiosity, is this an assignment or a learning thing? if its an assignment, you would need to follow the requirements given by your instructor.

#11

August 17th, 2007, 08:12 PM

mantai007

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Oh hmm i thought link list nodes need to be in a struct...

#12

August 17th, 2007, 08:30 PM

mantai007

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Yes it is an assignment...
Because i have to create the following classes...
"BookList"
"BookNode"
"Book"
and others.. thats why i got a little confused, so i wasnt sure to create 2 header files, one for booknode and booklist...

#13

August 17th, 2007, 11:04 PM

nattylife

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its totally possible to make a node out of a struct. but from the looks of your assignment, i think they want you to go with the class way that i mentioned. but you can always verify with your instructor. their requirements are what you need to base it on. it never hurts to ask advice from them on your design and such also to make sure you are on the same wavelength with the instructor.

#14

August 17th, 2007, 11:20 PM

mantai007

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yeah i made it into a class it seems simpler that way.. ill ask my tutor on monday and verify it..

#15

August 18th, 2007, 05:01 AM

mantai007

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ive implemented it now and it works.. i just looked at f'lar code and created BookNode as a class.. so its all working now.

thanks guys for the input.

Cannot access struct in h file

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