How to Initialize an Array of Objects Without a Default Constructor in C ?

Object Array Initialization without Default Constructor

When attempting to initialize an array of objects that lack a default constructor, programmers often encounter the error "X::X() is private within this context". This error arises because the default constructor is typically set to private to prevent unintentional object creation.

One solution is to employ placement-new, a low-level C operator that allows objects to be constructed directly into a block of memory. Here's an example:

class Car
{
    int _no;
public:
    Car(int no) : _no(no) // Initialize _no directly
    {
    }
};

int main()
{
    int userInput = 10;
    void *rawMemory = operator new[](userInput * sizeof(Car)); // Allocate raw memory
    Car *myCars = static_cast<Car *>(rawMemory); // Cast to Car *

    for (int i = 0; i < userInput; ++i)
    {
        new(&myCars[i]) Car(i); // Construct Car objects in-place using placement-new
    }

    // Destruct objects in reverse order
    for (int i = userInput - 1; i >= 0; --i)
    {
        myCars[i].~Car(); // Destroy the object using placement-delete
    }

    operator delete[](rawMemory); // Release raw memory

    return 0;
}

This technique provides a way to initialize arrays of objects without modifying the constructor's access specifier. It adheres to best practices by avoiding unnecessary default constructors while enabling flexible and efficient object creation.

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