[klippy]

Miu also said up above:

When you want to reference an object that already exists rather than create a new one

meaning that code like the following, seen often in HLSDK:

PHP Code:

CBaseEntity *pEntity = (CBaseEntity *)GET_PRIVATE(pent); 


which just returns entity's private data (edict_t::pvPrivateData) which could be any class that derives from CBaseEntity (that's just how things work in GoldSrc). By doing that, you are not creating a new instance of CBaseEntity, you are just pointing to an existing one, allowing you to alter entity's private data.

I really can't think of any good examples right now, sorry about that, hope these explanations are good enough to make you understand the concept a little bit better.

[asherkin]

Valve's code (and anything based on it like AMXX and SM) is NOT a good reference to be learning C++ from.
It is more C-like (pointer heavy rather than references and proper const-correctness) and avoids using the C++ STL.

[TheDS1337]

Originally Posted by asherkin Valve's code (and anything based on it like AMXX and SM) is NOT a good reference to be learning C++ from. It is more C-like (pointer heavy rather than references and proper const-correctness) and avoids using the C++ STL.

Oh! so that's why it focus more in using pointers because C is not powerful than C++

Originally Posted by KliPPy Miu also said up above: meaning that code like the following, seen often in HLSDK: PHP Code: CBaseEntity *pEntity = (CBaseEntity *)GET_PRIVATE(pent);  which just returns entity's private data (edict_t::pvPrivateData) which could be any class that derives from CBaseEntity (that's just how things work in GoldSrc). By doing that, you are not creating a new instance of CBaseEntity, you are just pointing to an existing one, allowing you to alter entity's private data. I really can't think of any good examples right now, sorry about that, hope these explanations are good enough to make you understand the concept a little bit better.

I got you in this one, thank you so much for your examples dude!

[TheDS1337]

Sorry for double post.

Being trying this code and I dont really know why it's not working... :/

PHP Code:

#include <iostream>

using namespace std;

class CFriends
{
public:
    char *pName, *pNickname;    

    CFriends() 
    { 
//        pName = new char[32];            THIS MAKES IT EVEN WORST
//        pNickname = new char[32];        THIS MAKES IT EVEN WORST
//        cout << "Allocating vars." << endl;        
    }

    ~CFriends() 
    {     
//        delete pName;
//        delete pNickname;
//        cout << "Deallocating vars." << endl;
    }
};

/*                                        DOENT WORK
const char *FirstToUpperchar(char *pText)
{
    if (*pText >= 'a' && *pText <= 'z')
        pText[0] = 'A' - 'a';

    return pText;
}
*/

int main()
{
    int friends;

    cout << "How many friends you have ?" << endl;
    cin >> friends;

    CFriends *pFriends = new CFriends[friends];

//    char *name = new char;                DOENT WORK
//    char *nickname = new char;            DOENT WORK
    char name[32], nickname[32];

    int iterator; 

    for (iterator = 0; iterator < friends; iterator++)
    {
        cout << "Enter friend name:";
        cin >> name;
        pFriends[iterator].pName = name;

        cout << "Enter his nickname:";
        cin >> nickname;
        pFriends[iterator].pNickname = nickname;

//        pFriends[iterator].pName = name;                Tried with *name too 
//        pFriends[iterator].pNickname = nickname;        with *nickname too 
    }

    cout << "Your friends are:" << endl;
    cout << "-----------------" << endl;

    for (iterator = 0; iterator < friends; iterator++)
    {
//        FirstToUpperchar(pFriends[iterator].pName);
//        FirstToUpperchar(pFriends[iterator].pNickname);

        printf("%d. %s (%s)\n", iterator + 1, pFriends[iterator].pName, pFriends[iterator].pNickname);
    }

    cout << "-----------------" << endl;

    system("PAUSE");

    delete[] pFriends;    
    return 0;
} 


[klippy]

If you are wondering why does it print same name and nickname for every friend, it's because CFriends::pName and CFriends::pNickname are just pointers, and by doing:

PHP Code:

pFriends[iterator].pName = name;
// ...
pFriends[iterator].pNickname = nickname; 


you are not copying the value of name and nickname to pName and pNickname, respectively, you are just making these 2 pointers point to these 2 arrays (name and nickname). What happens at the end of that loop is that all your CFriends (and you should've named it CFriend, not plural) objects have their pName and pNickname pointing to these 2 arrays, resulting in every friend object having the same values.
You should make CFriends::pName and CFriends::pNickname actual arrays, not just pointers, ie:

PHP Code:

char name[32];
char nickname[32]; 


Also, to copy the string, use strncpy() or any similar function. Also, your code is too "C-ish", you should just use std::string objects for strings, they will make your life much easier, but I guess you are here just learning how to use pointers correctly.

[Miu]

PHP Code:

#include <iostream>

using namespace std;

class CFriends
{
public:
    char *pName, *pNickname;

    CFriends()
    {
        pName = new char[32];
        pNickname = new char[32];
        //        cout << "Allocating vars." << endl;        
    }

    ~CFriends()
    {
        delete[] pName;
        delete[] pNickname;
        //        cout << "Deallocating vars." << endl;
    }
};

const char *FirstToUpperchar(char *pText)
{
    if (*pText >= 'a' && *pText <= 'z')
        pText[0] += 'A' - 'a';

    return pText;
}

int main()
{
    int friends;

    cout << "How many friends you have ?" << endl;
    cin >> friends;

    CFriends *pFriends = new CFriends[friends];

    //    char *name = new char;                DOENT WORK
    //    char *nickname = new char;            DOENT WORK
    char name[32], nickname[32];

    int iterator;

    for (iterator = 0; iterator < friends; iterator++)
    {
        cout << "Enter friend name:";
        cin >> name;
        strcpy(pFriends[iterator].pName, name);

        cout << "Enter his nickname:";
        cin >> nickname;
        strcpy(pFriends[iterator].pNickname, nickname);

        //        pFriends[iterator].pName = name;                Tried with *name too 
        //        pFriends[iterator].pNickname = nickname;        with *nickname too 
    }

    cout << "Your friends are:" << endl;
    cout << "-----------------" << endl;

    for (iterator = 0; iterator < friends; iterator++)
    {
        FirstToUpperchar(pFriends[iterator].pName);
        FirstToUpperchar(pFriends[iterator].pNickname);

        printf("%d. %s (%s)\n", iterator + 1, pFriends[iterator].pName, pFriends[iterator].pNickname);
    }

    cout << "-----------------" << endl;

    system("PAUSE");

    delete[] pFriends;
    return 0;
} 


[TheDS1337]

Thank you both for your answers! and I have to say yes I'm trying to understand the using of pointers and in same time I'm trying to use dynamic memory (that's why I didnt use std::string and I pointed *pName and *pNickname), since we don't know the exact buffer it can be bigger than 32 who know, I'm trying to get them dynamically, can you show me how can I make all of: pName, pNickname, name, nickname dynamically ? without giving them a size since putting [] instead of [32] ain't gonna work.

[klippy]

Here, I wrote some code to show you how you could load a string of indeterminate length. It's more C-like, and as I said, if I were to write real C++ code, I would use std::string and such.
This pretty much loads characters one-by-one, and if the buffer is close to overflowing, I increase its size. Sample output:


And here, even though you will see in following code that an array starts with size of 16, it can load much larger strings with no problem:


Code:

PHP Code:

#include <iostream>


char *firstToUpperchar(char *);

class CFriend {
private:
    char *pName;
    char *pNickname;

    // Default constructor is private, so the user has to use one below
    CFriend() {

    }

public:
    CFriend(char *name, char *nickname) : pName(firstToUpperchar(name)), pNickname(firstToUpperchar(nickname)) {
    }

    ~CFriend() {
        // Free memory allocated by readString
        free(pName);
        free(pNickname);
    }

    // These 2 methods are used so user can't change name and nickname
    char * const getName() const {
        return pName;
    }
    char * const getNickname() const {
        return pNickname;
    }
};

char *firstToUpperchar(char *str) {
    if (*str >= 'a' && *str <= 'z') {
        *str += 'A' - 'a';
    }

    return str;
}

// Caller is responsible for freeing memory allocated by this function
char *readString() {
    static const size_t sizeStep = 16; // We add 16 bytes to the allocated block each time it would overflow
    size_t memSize = 16; // We start with 16 chars
    size_t len = 0; // Length of the string we load in
    char *buf = (char *)malloc(sizeof(char) * memSize); // Allocate first memSize bytes
    char ch;

    for (;;) { // Infinite loop
        ch = getchar();
        if (ch == EOF || ch == '\n') { // We have reached the end, break out
            break;
        }

        buf[len++] = ch;
        // Buffer would overflow if we added one more char
        if (len == memSize) { 
            memSize += sizeStep; // Increase memory block size by sizeStep chars
            buf = (char *)realloc(buf, sizeof(char) * memSize); // And reallocate the array
        }
    }
    buf[len] = '\0';

    return buf;
}

int main(int argc, char *argv[]) {
    int friendsCount;
    std::cout << "How many friends do you have? ";
    std::cin >> friendsCount;
    std::cin.get(); // This just removes the trailing '\n' from the stream
    int i;

    // We are actually creating an array of POINTERS to CFriend, we are not initializing these objects, we'll do it later
    CFriend **pFriends = new CFriend*[friendsCount];

    char *name, *nickname;
    for (i = 0; i < friendsCount; i++) {
        std::cout << "Name of friend #" << (i + 1) << ": ";
        name = readString();
        std::cout << "Nickname of friend #" << (i + 1) << ": ";
        nickname = readString();

        // Here is where we actually create an object
        pFriends[i] = new CFriend(name, nickname);
    }

    std::cout << "Your friends are:" << std::endl;
    std::cout << "-----------------" << std::endl;

    for (i = 0; i < friendsCount; i++) {
        std::cout << (i + 1) << ". " << pFriends[i]->getName() << " (" << pFriends[i]->getNickname() << ")" << std::endl;
    }

    std::cout << "-----------------" << std::endl;

    getchar(); // This works like system("PAUSE"), but should be more platform-independant
    delete[] pFriends;
    return 0;
} 


[TheDS1337]

Oh, really nice! this is exactly what I wanted a dynamic buffer. thank you for your work m8!