C / C++ / MFC

Wikipedia:

In object oriented programming languages, encapsulation is used to refer to one of two related but distinct notions, and sometimes to the combination thereof:
- A language mechanism for restricting direct access to some of the object's components.
- A language construct that facilitates the bundling of data with the methods (or other functions) operating on that data.

Richard MacCutchan wrote:

There is no mechanism for hiding members of a struct.

struct car;

struct car
{
private:
    char make[10];
    char model[10];
    int year;

public:
    char *getMake();
    char *getModel();
    char *getYear();
};

struct CarPrivate;

struct Car 
{
    struct CarPrivate* priv;
};

extern char* GetYear(struct Car* car);

struct CarPrivate 
{
    int year;
};

int GetYear(struct Car* car) 
{
    return car->priv->year;
}

void main( void )
{
    struct Car* car = some_method_to_create_car();
    int year = car->priv->year; // error
}

Richard MacCutchan wrote:

...since you can still access the data directly...

Richard MacCutchan wrote:

If you have the definitions in a header...

Richard MacCutchan wrote:

At the risk of repeating myself, that is not going to work.

Richard MacCutchan wrote:

...and not provide the struct definition to the user...

Richard MacCutchan wrote:

But that means the user cannot allocate any space for the data in the first place.

struct Car* car = some_method_to_create_car();

David Crow wrote:

I really want to know what I'm doing wrong.

/* In ExpContainer.h */

/* this is one possibility for a handle */
#define EXPHANDLE void*

EXPHANDLE ExpContainer_Create(size_t data_size, size_t count);
void ExpContainerDestroy(EXPHANDLE hExpContainer);
size_t ExpContainer_Insert(EXPHANDLE hExpContainer, void*, size_t pos);
size_t ExpContainer_Append(EXPHANDLE hExpContainer, void*); // or push_back
/* etc. */

/* In ExpContainer.c */

/* example container */
struct ExpContainer
{
    /* hidden data can be anything you wish */
    size_t data_size_; /* size passed as argument to create method */
    size_t size_; /* current number data_size_ elements space allocated */
    size_t used_; /* current number of elements */
    void* data_;  /* just one possibility for storage */

    /* the handle/pointer will be pointing to this value */
    unsigned signature_; /* in case you want handle validation */
};

EXPHANDLE ExpContainer_Create(size_t data_size, size_t count);
{
   /* create a new container */
   struct ExpContainer* pContainer = malloc(sizeof(struct ExpContainer));

   /* continue with other initiation */

   /* return a handle to the user */
   return (EXPHANDLE)(pContainer  + offsetof(signature_));
}

Aakashdata wrote:

Why C is not popular among developers?

manoharbalu wrote:

The problem is when I click on the view, it throws an assertion "Debug Assertion Failed at line: 252 in viewcore.CPP".

manoharbalu wrote:

The problem is when I click on the view...I have added the below code for selection of tabs.