C / C++ / MFC

17-Jun-04 1:53

Hi!

I have had a problem yesterday and written code as suggested. I have it now working.

I have a class CBook and another class CSubject. CSubject has a member which is a CList of CBook pointers. I want to serialize my CSubject object together with any CBook objects it contains.

I wrote my code like was suggested and inherited both from CObject. I overloaded the CObject Serialize() member function in both CBook and CSubject and added the MFC serialization macros. When serialize a CSubject object to disk the data file that is created contains all the data I want. The data is the subject and all the books I add to the subject. So that works very well but now I come to deserialize from disk and I have problems. How do I know how to create enough books when I am calling the Serialize() function? I thought I must be able to in the CSubject::Serialize() function count the books in the list first and store the number. When I deserialize I then know how many to try to get?

Is this the right way to do what I want?

What is really the point in the COBject inheritance? What value must it give to me as I think I am doing all the work in my Serialize() functions myself!

Rodrigo Pinto Pereira de Souza17-Jun-04 2:20

17-Jun-04 2:20

I suggest you to change the architecture of your class to :

This is corrected way to serialize a List Object.

I Write only the important parts to serialize a list.

//Header File .h
class CBook: public CObject
{
public:
DECLARE_SERIAL(CBook)
CBook();

// You must implement CopyConstructor and = operator.
CBook(const CBook& objSource);
CBook& operator=(const CBook& objSource);

virtual void Serialize(CArchive& ar); // Implement your serialization
public:
CString m_sName;
};

class CBookList: public CList<cbook, cbook&="">
{
public:
CBookList();
virtual ~CBookList();
}

template <> void AFXAPI SerializeElements <cprvfile>
(CArchive& ar, CPrvFile* pNewPrvFile, int nCount);

class CSubject : public CObject
{
public:
DECLARE_SERIAL(CSubject)
CSubject();
virtual void Serialize(CArchive& ar); // Implement your serialization
public:
CString m_sName;
CBookList m_BookList;
};

// Implementation File .cpp

// The Secret of Serialize List Elements !!!!
template <> void AFXAPI SerializeElements <cbook>
(CArchive& ar, CBook* pNewBook, int nCount)
{
for (int i = 0; i < nCount; i++, pNewBook++)
{
// Serialize each CBook object
pNewBook->Serialize(ar);
}
}

Enjoy it Cool | :cool:

Rodrigo Pinho Pereira de Souza

Anonymous17-Jun-04 2:54

17-Jun-04 2:54

Thank you.

This looks hard. Is there any benefit over what I was suggesting I do with storing the number of objects so I know how many to restore?

Also what about using CObList? This provides a Serialize() function which I may be able to call. Will this restore my list of objects with no further work? I think I could have a data member in my CSubject class which is of type CObList. When CSubject::Serialize() is called I must then only have to call CObList::Serialize() yes?

I am quite confused with all this. I can make it work now though and it looks good but then I hear that there are other ways that can be better though not easier Smile | :)

I also still do not understand why CObject provides any function to me. As I can tell it just gives me a Serialize() function as a declaration which I must then write anyway.

Rodrigo Pinto Pereira de Souza17-Jun-04 7:46

17-Jun-04 7:46

The benefit is that with this implementation, you will using a real Object Oriented Concepts.

I think that is more clear to understand, and easy to implement than use CObList Member Variable.

Look in MSDN for template SerializeElements, and you will see that Microsoft recommend use this template when you want to serialize element. Is more efficient and trustable.

If you want, I can send you an example for Serialization of List. I will write an article, that I will use this example.

mail me Cool | :cool:

: rpinho@mobiledeveloperspace.de

regards,

Rodrigo Pinho Pereira de Souza

Antony M Kancidrowski17-Jun-04 2:24

17-Jun-04 2:24

You could Serialize out the number of books written before the serialized books. Then on deserialize read the number of books, create the books and read them back in.

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fuity and sweet.
I'm jelly, what am I? - David Williams (Little Britain)

Anonymous17-Jun-04 2:55

17-Jun-04 2:55

Yes that is what I thought I must do. I think it is very easy to do this way but someone else has suggested using a CList member and to call its serialization support.

Rodrigo Pinto Pereira de Souza17-Jun-04 7:49

17-Jun-04 7:49

This works, but personally, I only use this method to serialize data which the datatype is not supoorted by Serialization, like TCHAR*.

regards,

Rodrigo Pinho Pereira de Souza

Unsigned Char to char*

Wender Oliveira17-Jun-04 1:46

Wender Oliveira

17-Jun-04 1:46

Hello people, I'm trying to learn a few more of C++ once that I know another language. My question is... I have an array of unsigned char like this "unsigned char myArr[6]" and I want to get these values and show them into a Static Text (Visual C++) and I don't know how to convert these unsigned char array to char* or any type of "string". Can anyone help me?

thanks!

Wender Oliveira
.NET Programmer

Rodrigo Pinto Pereira de Souza17-Jun-04 2:03

17-Jun-04 2:03

Try it.

char myArr[6];
SetDlgItemText(ID_EDIT, myArr);

If you are beginner with Visual C, I suggest you to use MFC classes, Then, you will get CString class, that are similar to String from .Net

Enjoy it. Cool | :cool:

Rodrigo Pinho Pereira de Souza

toxcct17-Jun-04 4:21

toxcct

17-Jun-04 4:21

pinhopro wrote:
SetDlgItemText(ID_EDIT, myArr);
no way. it is only if you consider that one of the 6 chars of the array contain a '\0'

no, to display each char, prefer that :

CString str;
<font style="color:blue;">char </font>myArr[6];
<font style="color:green;">//...</font>
str.format(<font style="color:purple;">"%c%c%c%c%c%c"</font>, myArr[0], myArr[1], myArr[2], myArr[3], myArr[4], myArr[5]);
<font style="color:green;">//...</font>
((CStatic*)GetDlgItem(IDC_MYSTATIC))->SetWindowText(str);

TOXCCT >>> GEII power

Anonymous17-Jun-04 9:44

17-Jun-04 9:44

Wender, I have not logged many hours on Visual C++ .net but I think what you are asking to do is called a cast. Changing one type to another. However, an array really is a pointer as your myArr[0] would be the address of the array. So if you said printf("%s\n", myArr); your getting the all 6 items as opposed to: printf("%s\n", myArr[1]); where you will get the first character.

John R. Shaw17-Jun-04 12:19

John R. Shaw

17-Jun-04 12:19

Anonymous wrote:
myArr[0] would be the address of the array

myArr would be the address, it is an unsigned char*. myArr[0] is the first character in the array.

Anonymous wrote:
So if you said printf("%s\n", myArr); your getting the all 6 items

No! There is only room for 6 characters in array and the last character must be '\0', so you would be printing only the first characters

Anonymous wrote:
printf("%s\n", myArr[1]); where you will get the first character.

This is just wrong! myArr[1] is the second, not the first charater and it is not a string pointer, so the results will be undefined. The %s expects a string pointer not a character value.

INTP

Difference between Structures and Classes

John R. Shaw17-Jun-04 12:30

John R. Shaw

17-Jun-04 12:30

Assuming you want to display all 6 characters then you need to set the array size to 7, since the last character must be '\0'.

Exmaples:
1) unsigned char myArr[7]={"012345\0"};
2) unsigned char myArr[7];
myArr[0] = '0';
myArr[1] = '1';
myArr[2] = '2';
myArr[3] = '3';
myArr[4] = '4';
myArr[5] = '5';
myArr[6] = '\0';

Now it you want a char* insted of a unsigned char* just cast it: (char*)myArr. This is safe because both unsigned char and char are the same size.

There are other ways, but why make life difficult.

INTP

Zeeshan Bilal17-Jun-04 1:32

Zeeshan Bilal

17-Jun-04 1:32

HI,

Wt r the Differnces between Structures and Classes

one i know is its Defualt Access specifiers.

in structure it is Public. and in Class it is Private.

tell me more

thanx

Trollslayer17-Jun-04 1:38

Trollslayer

17-Jun-04 1:38

Basic difference - structures only have data, classes also have methods.

The tigress is here Big Grin | :-D

Zeeshan Bilal17-Jun-04 1:52

Zeeshan Bilal

17-Jun-04 1:52

As i think we can add methods to Structure tooo
is it ?

any other difference
Assume it was interview Question to me

Antony M Kancidrowski17-Jun-04 2:09

17-Jun-04 2:09

You can add methods to structures. I can only see that you can't inherit from structures. No polymorphism. Smile | :)

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fuity and sweet.
I'm jelly, what am I? - David Williams (Little Britain)

Zeeshan Bilal17-Jun-04 2:18

Zeeshan Bilal

17-Jun-04 2:18

it means simply that if we not inherit structures ,,
then we can not attain the Concepts of OOP with structers.. is it.

any other difference ??

thanx

Antony M Kancidrowski17-Jun-04 2:40

17-Jun-04 2:40

I can't think of any other difference.

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fuity and sweet.
I'm jelly, what am I? - David Williams (Little Britain)

David Crow17-Jun-04 3:01

David Crow

17-Jun-04 3:01

Antony M Kancidrowski wrote:
I can only see that you can't inherit from structures.

Have you not seen the CRect class? It is derived from the tagRECT struct. This is perfectly legal:

struct s
{
};
 
class c : public s
{
};

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

Antony M Kancidrowski17-Jun-04 10:07

17-Jun-04 10:07

That isn't a struct inheriting from a struct, which is what I meant. Point taken however.

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fuity and sweet.
I'm jelly, what am I? Muse on it further, I shall return! - David Williams (Little Britain)

David Crow17-Jun-04 10:11

David Crow

17-Jun-04 10:11

Antony M Kancidrowski wrote:
That isn't a struct inheriting from a struct, which is what I meant.

But this is:

struct s1
{
};
 
struct s2 : public s1
{
};

"When I was born I was so surprised that I didn't talk for a year and a half." - Gracie Allen

Antony M Kancidrowski17-Jun-04 10:15

17-Jun-04 10:15

OK, I have learnt something new. I have never seen such a struct definition. Noted and commited to memory.

Thanks David

Ant.

I'm hard, yet soft.
I'm coloured, yet clear.
I'm fuity and sweet.
I'm jelly, what am I? Muse on it further, I shall return! - David Williams (Little Britain)