How to use an array of string in c++? - c++

Question

I need to make an array of string where I can store either 3 or 5 words like {"banana, peach, pear"}, or {"orange", "pear", "silantro", "ginger", "mandarine"}.
I'm confused if I should make an array of string pointer(to dynamically allocate the memory depending on the size of the array-3 or 5), or just have an array of string with the statically allocated memory of 5. And how to initialize it/set it to null/use it in the constructors.
I'm not allowed to use vector.
When I declared an array of size 5, the problem started in the default constructor.
I don't know how to set it to null...
// string multiple_fruits[5]
// multiple_fruits[] = { nullptr, };
So I'm using an array of string pointer here, is there a better way?
What am I doing wrong?? HAAAALP
//.h file
class Fruit {
char* single_fruit;
string* multiple_fruits;
int num_Fruits;
};
//.cpp file
Fruit::Fruit() {
single_fruit = nullptr;
multiple_fruits = nullptr;
num_Fruits = 0;
}
Fruit::Fruit(const char* singlefruit, string* multiplefruits, int numFruits) {
single_fruit = new char[strlen(singlefruit) + 1];
strcpy_s(single_fruit, strlen(singlefruit) + 1, singlefruit);
multiple_fruits = new string[numFruits];
for (int i = 0; i < numFruits; i++) {
multiple_fruits[i] = multiplefruits[i];
}
num_fruits = numFruits;
}
int main() {
Fruit A;
A("apple", {"banana", "peach", "pear"}, 3)
Fruit B;
B("lemon", {"orange", "pear", "silantro", "ginger", "mandarine"}, 5);
return 0;
}

Answer 1

My approach is to use std::string and std::initializer_list for this:
#include <string>
#include <initializer_list>
class Fruit {
public:
Fruit(const std::string &singlefruit, const std::initializer_list<std::string> &multiplefruits) : single_fruit{singlefruit}, multiple_fruits{new std::string[multiplefruits.size()]}, num_Fruits{multiplefruits.size()} {
for (std::size_t i = 0; i < num_Fruits; ++i) {
multiple_fruits[i] = *(multiplefruits.begin() + i);
}
}
~Fruit() {
delete[] multiple_fruits;
}
private:
std::string single_fruit;
std::string *multiple_fruits;
std::size_t num_Fruits;
};
int main() {
Fruit A("apple", {"banana", "peach", "pear"});
Fruit B("lemon", {"orange", "pear", "silantro", "ginger", "mandarine"});
}
I allocated memory for the elements and deleted the memory in the destructor.
You can't declare a variable in one line and call the constructor in the next line.

Answer 2

Here's one way using a proper declaration of the array argument to the constructor.
#include <algorithm> // std::copy
#include <iterator> // std::begin, std::end
#include <string>
#include <iostream>
template<size_t N>
class Fruit {
public:
Fruit();
Fruit(const std::string& singlefruit, const std::string (&multiplefruits)[N]);
size_t size() const;
private:
std::string single_fruit;
std::string multiple_fruits[N];
};
template<size_t N>
Fruit<N>::Fruit() {}
template<size_t N>
Fruit<N>::Fruit(const std::string& singlefruit, const std::string (&multiplefruits)[N])
: // colon indicates the start of the member initializer list
single_fruit(singlefruit)
{
std::copy(std::begin(multiplefruits), std::end(multiplefruits), multiple_fruits);
}
template<size_t N>
size_t Fruit<N>::size() const { return N; }
int main() {
Fruit A("apple", {"banana", "peach", "pear"});
std::cout << A.size() << '\n';
Fruit B("lemon", {"orange", "pear", "silantro", "ginger", "mandarine"});
std::cout << B.size() << '\n';
}
Output:
3
5