initializing an passing a string array as a parameter - c++

Question

Can I initiate a string array and pass it as a function that initializes it. I know this sounds redundant, but basically I want to initiate a string array and then pass it to a variable so that I can use it later? Something like this:
This is the .h:
class ScreenBasics{
void setupAnswers(int &_numberOfAnswers, string *_answersText);
string *answersText;
{
This will be the implementation .cpp
void ScreenBasics::setupAnswers(int &_numberOfAnswers, string *_answersText){
answersText = _answersText; // this is where I get confused cause I don't know if I should initiate my string pointer using new like answersText = new string(_numberOfAnswers);
{
so in the main.cpp I can do something like this:
int main( ) {
ScreenBasics basics;
int numberOfAnswers = 4;
string newAnswers [] = { "Good", "Superb", "Great", "Perfect"};
basics.setupAnswers(numberOfAnswers, newAnswers);
// let's say I want to call some of those answers later
for ( int i = 0; i < numberOfAnswers; i++){
cout << basics.answersText[i] << endl;
}
}
Thanks!

Answer 1

Have you thougt about using structs? Both classes and structs can have a mixture of public and private members, can use inheritance, and can have member functions. I would recommend using structs as plain-old-data structures without any class-like features, and using classes as aggregate data structures with private data and member functions.
Your code would look like the following:
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
struct movies_t {
string title;
int year;
} mine, yours;
int main ()
{
string mystr;
mine.title = "2001 A Space Odyssey";
mine.year = 1968;
cout << "Enter title: ";
getline (cin,yours.title);
cout << "Enter year: ";
getline (cin,mystr);
stringstream(mystr) >> yours.year;
cout << "My favorite movie is:\n ";
printmovie (mine);
cout << "And yours is:\n ";
printmovie (yours);
return 0;
}
void printmovie (movies_t movie)
{
cout << movie.title;
cout << " (" << movie.year << ")\n";
}
Please let me know if you have any questions!

Answer 2

It sounds like your class should use a constructor to initialize the pointer.
class ScreenBasics
{
ScreenBasics(std::string* _answersText, std::size_t size)
: answersText(new std::string[size])
{
// copy values from _answersText to answersText
}
};
Note that since you are allocating a resource dynamically, you will need to implement The Rule of Three: that is, you need to create a copy-constructor, copy-assignment operator and destructor. This is because their default implementations do not semantocally conform to our requirements. For instance, the default copy-constructor and copy-assignment operator perform shallow copies (that is, they copy the pointer but not what it points to). Also, the destructor doesn't free the memory allocated my new[]. You will need to provide your own definition of the destructor that calls delete[].
Fortunately, all this can be avoided by using the standard library container std::vector, which is a dynamic array class that handles the memory allocation for you. The default implementations of the aforementioned constructors will correctly copy/copy-assign a vector if the need be:
class ScreenBasics
{
ScreenBasics(std:vector<std::string> _answersText)
: answersText(_answersText)
{
}
};
Notice that the size also didn't have to be passed as a parameter. A vector maintains its size internally.