Calling a Function in a Class with Parameters C++ - c++

Question

I'm practicing in order to better understand dynamic arrays and using them in a class. However, I'm struggling to call my functions inside the class. I have no issue with my int size variable, but my int myArray variable is giving me problems. I get the error "expected a member name" when I try to call my void functions in my main function. Are arrays not allowed to be used in this situation?
#include <iostream>
using namespace std;
class myClass
{
public:
int size;
int* myArray = new int[size];
void storeData(int& size, int (&myArray)[]);
void printData(int& size, int(&myArray)[]);
};
void myClass::storeData(int& size, int(&myArray)[])
// Stores array data.
{
cout << "Enter Size of the array: ";
cin >> size;
// User determines array size.
for (int x = 0; x < size; x++)
{
cout << "Array[" << x << "]: ";
cin >> myArray[x];
// User determines array values.
cout << endl;
}
}
void myClass::printData(int &size, int(&myArray)[])
// Displays values of the array.
{
cout << "Value of the arrays are: ";
for (int x = 0; x < size; x++)
{
cout << myArray[x] << " ";;
}
delete[]myArray;
}
int main()
{
myClass object;
object.storeData(object.size, object.(&myArray)[]);
// E0133 expected a member name.
object.printData(object.size, object.(&myArray)[]);
// E0133 expected a member name.
}

Answer 1

There are a couple issues here, I will try to address all of them.
When passing an array to a function, never use [] syntax. In C and C++, arrays decay to pointers, so we do not need [] nor &.
This is valid syntax to pass an array:
int my_array [] = {1,2,3,4};
my_function(my_array, 4);
...
void my_function(int * array, size_t size)
{
//Iterate over the array or do something...
}
In addition, if a function exists within a class, it can access class members freely, meaning we do not have to pass them in at all. See the following change to your code:
void myClass::storeData(int size)
// Stores array data. We do NOT need a pointer to the object array, we already have it!
{
cout << "Enter Size of the array: ";
cin >> size;
// User determines array size.
for (int x = 0; x < size; x++)
{
cout << "Array[" << x << "]: ";
cin >> myArray[x];
// User determines array values.
cout << endl;
}
}
Lastly, dynamic sized arrays must be allocated dynamically. Do not use int* myArray = new int[size]; in your class definition, because size is not yet initialized. Instead, use a constructor or use your store_data function to allocate the memory.
class myClass
{
public:
size_t size;
int * myArray; //Do not allocate anything here...
myClass(size_t size)
{
this->size = size;
myArray = new int[size];
}
};
You can get the size however you want, via user input, etc. and pass this to the constructor or an allocator function like storeData.