Thread: Arrays of pointers...

Originally Posted by Programmer_P

Hello,
I have a problem. I need to make an array of pointers, without knowing beforehand the size of the array. Is this possible?

Code:

const char* arrayOfPointers[];

Sure:

Code:

int main( void )
{
    const char** arrayOfPointers = 0;
    // sometime later
    unsigned size = 1024;
    arrayOfPointers = new const char*[ size ];
    // do something usefull
    delete [ ] arrayOfPointers;
}

Thing is, though, you have to remember to delete the memory. A much better way is to use an std::vector, or similar, eg:

Code:

#include <vector>

int main( void )
{
    std::vector< const char* > arrayOfPointers;
    // sometime later
    unsigned size = 1024;
    arrayOfPointers.resize( size );
    // do something useful...memory will be deleted by vector object...
}

if it is an array of char * ptrs sure...

How about this?

Code:

string* str = NULL;
str = new string;
*str = "Yes, a string...\n";
*str += "Yes, another string...\n";
*str += "Yes, even another string...\n";
int sizeOfStr = str->size();
char* arrayOfPointers[] = NULL;
//several code lines later...
arrayOfPointers = new char*[sizeOfStr];
string* anotherStr = NULL;
anotherStr = new string;

void doStuff();
void doStuff() {
  for (int = 0; i < sizeOfStr; i++) {
    while (str->at[i] != '\n') {
      *anotherStr += str->at[i];
    }
    *arrayOfPointers[i] = *anotherStr->data();
    anotherStr = NULL; //reset this pointer
  }
}

int main() {
  doStuff();
  int sizeOfArray = sizeof(arrayOfPointers);
  for (int = 0; i < sizeOfArray; i++) {
    cout<< *arrayOfPointers[i] <<endl;
  }
  
  delete str;
  delete [] arrayOfPointers;
  delete anotherStr;
  return 0;

}

Would the output be:

Yes, a string...
Yes, another string...
Yes, even another string...

?

Originally Posted by tabstop

Why are you asking us? Don't you have a computer of your own? Why not try it and see?

For others' benefit.
For the record, I tried it (though obviously including <string> and <iostream>), but it didn't compile. It said it expected constructor, destructor, or type conversion before the '=' token for the "string* str = NULL" line, as well as several lines after that. After changing the string pointer to a string object, it now says 'string' does not name a type, so obviously its not seeing the string class's definition for some reason, and I don't know why, seeing as I included it....

Originally Posted by tabstop

The <string> header doesn't give you a type called string. It does, however, give you a type called std::string.

Oh right..duh. I should have guessed that.
Thanks.

However, even after adding the line:

Code:

using namespace std;

I still get the same errors about expecting constructor before '=' token.

Originally Posted by tabstop

The code you posted works perfectly fine:

Code:

#include <string>

int main() {
    std::string *str = NULL;
    return 0;
}

is a marvelous piece of code that compiles with no errors.

Well, it didn't for me. Still, multiple errors.
Evidently, my compiler doesn't seem to like when I try to create a "new" string outside any function.

Also note that the code was only an example anyway. In the real code that I was really asking about, all variables (including the ones that are created in dynamic memory) are created inside functions.