Dynamic Array Using Strings in a Function Issues

Question

I'm trying to run a dynamic array that employs strings, but when I push it through a function I get compile errors 'dynamicArray': undeclared identifier, 'string':undeclared identifier, and illegal use of type 'void'. All of these errors point to the header for some reason.

I call the pointer here:

string* dynamicArray = NULL;

I call the function here:

populateArray(dynamicArray);

What is in the header:

void populateArray(string *&dynamicArray);

The function:

void populateArray(string *&dynamicArray)
{
char decide;
bool moreStrings = true;
int counter = 0;
while (moreStrings == true)
{
    counter ++;
    dynamicArray = new string[counter];
    cout << "\nEnter your string here:";
    cin >> dynamicArray[counter - 1];
    cout << "\nDo you want to enter another string? Y/N:";
    cin >> decide;
    decide = toupper(decide);
    if (decide == 'N')
    {
        moreStrings = false;
    }
}
}

PS: vector may be better, but I'm afraid that isn't an option. Please only offer fixes that deal with pointers.

Where do you do "string* dynamicArray = NULL;" ? Are you sure it is not put mistakenly in a place out of a function scope? — Nick Louloudakis, Feb 13 '14 at 07:39
string is from the std string library ? you should add header file #include using namespace std, and It seems the new string array will cover the older one — michaeltang, Feb 13 '14 at 07:40
Until the user enters 'N' you keep overwriting the dynamicArray pointer without deleting it prior to that. — rozina, Feb 13 '14 at 07:42
My problems were caused by lacking using namespace std in the header file. — user2954467, Feb 13 '14 at 07:45
Note that `using namespace std` is not advisable. Just type `std::string` instead of `string` :) — rozina, Feb 13 '14 at 07:47
That is just one of problems. There are more than two logic errors — Sung, Feb 13 '14 at 07:47

score 0 · Answer 1 · answered Feb 13 '14 at 07:42

0

You need to include <string> in your header file.

BTW, there might be potential memory leak in your code, if moreString is true, dynamicArray will point to another new string array, without deleting current one.

answered Feb 13 '14 at 07:42

jeffw

11
2

Also don't forget `using std::string`. – rozina Feb 13 '14 at 07:44
Yes, actually `using namespace std;` is enough. – jeffw Feb 13 '14 at 08:43
But is not recommended, since you bring in the whole std namespace. – rozina Feb 13 '14 at 08:46

score 0 · Accepted Answer · answered Feb 13 '14 at 07:45

With #include <string> and using namespace std; added, it compiles just fine for me.

#include <string>
#include <iostream>
using namespace std;

void populateArray(string *&dynamicArray);

int main(){
    string* dynamicArray = NULL;
    populateArray(dynamicArray);
    return 0;
}

void populateArray(string *&dynamicArray)
{
    char decide;
    bool moreStrings = true;
    int counter = 0;
    while (moreStrings == true)
    {
        counter ++;
        dynamicArray = new string[counter];
        cout << "\nEnter your string here:";
        cin >> dynamicArray[counter - 1];
        cout << "\nDo you want to enter another string? Y/N:";
        cin >> decide;
        decide = toupper(decide);
        if (decide == 'N')
        {
            moreStrings = false;
        }
    }
}

score 0 · Answer 3 · edited May 23 '17 at 12:20

I see a bigger problem than the missing include and the using clause...

You wrote:

dynamicArray = new string[counter];

But this will allocate a new memory area for you every time. It does not copy the previously allocated elements. IF you don't want to use std::vector, you need to use malloc for the first element and than call realloc to copy your previously allocated data to your new one.

Check this form more info: What is C++ version of realloc(), to allocate the new buffer and copy the contents from the old one?

Dynamic Array Using Strings in a Function Issues

3 Answers3