Passing a pointer to an array of strings in to a function

[jsans]

Dear,

I have check some post but I can not see what is happening to me. I am experimenting with pointers, arrays and functions to learn how to use it. I have initialized a simple pointer to an string array using dynamic allocation (*p_names)(to further expand the array later), I want to pass that pointer (*p_names)as an argument for the function IntrNewName, but I am not able to do it. What is happening? How I can pass a pointer to an array of string (for example cointaining different names )into a function? When I change the type to char instead of string it just works fine (see second program after % row) of course with a single char.

#include <iostream>
#include <string>

void IntrNewName(int *p_UsersNumber,int* p_Names);//Or it should be: void IntrNewName(int *p_UsersNumber,string* p_Names);    ?????'

using namespace std;

int main()
{
    int UsersNumber=1;
    int *p_UsersNumber=&UsersNumber;
    string *p_Names=new string [UsersNumber];
    IntrNewName(p_UsersNumber,p_Names);
    //print to see the result of IntrNewName
    cout<<*p_UsersNumber;
    cout<<p_Names[0];

}

void IntrNewName(int *p_UsersNumber,int* p_Names)
{
    cout<<"Please introduce new name:"<<endl;
    cin>>p_Names[*p_UsersNumber-1];
    *p_UsersNumber+=1;
}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

USING char

#include <iostream>
#include <string>

void IntrNewName(int *p_UsersNumber,char* p_Names);

using namespace std;

int main()
{
    int UsersNumber=1;
    int *p_UsersNumber=&UsersNumber;
    char *p_Names=new char [UsersNumber];
    IntrNewName(p_UsersNumber,p_Names);
    //print to see the result of IntrNewName
    cout<<*p_UsersNumber;
    cout<<p_Names[0];

}

void IntrNewName(int *p_UsersNumber,char* p_Names)
{
    cout<<"Please introduce new name:"<<endl;
    cin>>p_Names[*p_UsersNumber-1];
    *p_UsersNumber+=1;
}

[DivineLight]

The problem is that what you want is a string array, but in your second example you use a char array, which is similar to a single string. Also, it seems unnecessary to pass UsersNumber using a pointer; a reference should be sufficient.

//Or it should be: void IntrNewName(int *p_UsersNumber,string* p_Names);    ?????' 

Yes.

#include <iostream>
#include <string>

using namespace std;

void IntrNewName(int &usersNumber, string *p_Names);

int main()
{
    int usersNumber = 1;
    string *p_Names = new string[usersNumber];
    IntrNewName(usersNumber, p_Names);
    //print to see the result of IntrNewName
    cout<<usersNumber;
    cout<<p_Names[0];

}

void IntrNewName(int &usersNumber, string *p_Names)
{
    cout << "Please introduce new name: ";
    cin >> p_Names[usersNumber - 1];
    cout << endl;
    usersNumber += 1;
}

[GRex2595]

I haven't seen where this is going yet, but please remember to be careful when you're working with your array. If you don't remember to resize it, you might run into trouble.

[jsans]

Thank you for your replies.

Finally I have figured out what happened when I was checking the DivineLight code. The function prototype should be after "using namespace std;" to correctly compile it. I had seen this error yesterday a hundred times. The new code is, using pointers:

#include <iostream>
#include <string>

using namespace std;

void IntrNewName(int *p_UsersNumber, string *p_Names);

int main()
{
int UsersNumber=1;
int *p_UsersNumber=&UsersNumber;
string *p_Names=new string [UsersNumber];
IntrNewName(p_UsersNumber,p_Names);
//print to see the result of IntrNewName
cout<<UsersNumber;
cout<<p_Names[0];

}

void IntrNewName(int *p_UsersNumber,string *p_Names)
{
cout<<"Please introduce new name:"<<endl;
cin>>p_Names[*p_UsersNumber-1];
*p_UsersNumber+=1;
}


At this point I am trying to learn programing in C++ by my own. The piece of code where I had the doubt it was the starting point of some program to learn how to use pointers in dynamic memory allocation but I got stuck at the point where I had to pass the pointer to string array to the function.

Usually at every step I take I try to see the result to know if the code works up to that point.

Now I can continue with my program. Every time you introduce a new name, the array will increase their size dynamically to allocate the new name. It sounds not very sophisticated but my objective now is understand what I am doing. If I have to say the truth I do not see a clear difference between pointers and references yet!

Thank you again for your help!