Question

I have very technical question, I was working with C, and now I’m studying C++,
if I have for example this class

class Team {
private:
   list<Player> listOfPlayers;
public:
    void addPlayer(string firstName, string lastName, int id) {
        Player newPlayer(string firstName, string lastName, int id);
            listOfPlayers.push_back(Player(string firstName, string lastName, int id));
    }
};

this is a declaration of the Player:

class Player{
private:
    string strLastName;      
    string strFirstName;     
    int nID;                
public:
    Player(string firstName, string lastName, int id);

};

and this is my constructor of Player:

Player::Player(string firstName, string lastName, int id){
    nId = id;
    string strFirstName = firstName;
    string strLastName = lastName;
}

so my question is when I call function addPlayer what exactly is going on with program,

in my constructor of Account do I need to allocate new memory for new Player(cause in C I always use malloc) for strFirstName and strLastName, or constructor of string of Account and STL do it without me, thanks in advance (if you don’t want to answer my question please at least give me some link with information) thanks in advance

Answer 1

Here’s a “correct” implementation of what you have now:

#include <list>
#include <string>

class Player
{ 
private: 
    std::string strLastName;       
    std::string strFirstName;      
    int nID;                 
public:
    // You should pass std::strings to functions by const reference.
    // (see Kirill V. Lyadvinsky's comment to OP's question)
    Player(const std::string& firstName, const std::string& lastName, int id); 
};

// What follows after the colon is called the initializer list.
Player::Player(const std::string& firstName, const std::string& lastName, int id)
    : strFirstName(firstName), strLastName(lastName), nID(id) {}

class Team
{ 
private: 
    std::list<Player> listOfPlayers; 
public: 
    void addPlayer(const std::string& firstName,
        const std::string& lastName, int id)
    { 
        // Constructs a Player instance and adds it to the list.
        listOfPlayers.push_back(Player(firstName, lastName, id)); 
    } 
};

The push_back() function of list allocates a new node that holds the Player instance and pointers to other nodes, so you have sort of a “chain” of Player instances.

For your question about Account, if you have this:

class Account
{
private:
    std::string strFirstName;
    std::string strLastName;
};

Then you don’t need to worry about allocating/freeing memory for the character arrays, for std::string will handle that for you.