I can't add a new element to dynamic array-CodePudding

There is something wrong with the expand() method.

#include <iostream> 

struct obj
{
    int fInt;
    float fFloat;
};

template <typename T>

class dynamicArray {
private:
    T* myArray;
    int elements;
    int size;

public:
    dynamicArray();
    void add(T dane);
    void expand();
    void init(int el);
    T get(int index);
};

template <typename T>
dynamicArray<T>::dynamicArray()
{
    this->size = 1;
    this->elements = 0;
    this->myArray = new T[this->size];
    init(this->elements);
}

template <typename T>
T dynamicArray<T>::get(int index)
{
    return this->myArray[index];
}

template <typename T>
void dynamicArray<T>::init(int el)
{
    for (size_t i = el; i < this->size; i  )
    {
        this->myArray[this->elements] = nullptr;
    }
}

template <typename T>
void dynamicArray<T>::expand()
{
    this->size *= 2;
    T* tempArr = new T[this->size];
    for (int i = 0; i < this->elements; i  )
    {
        tempArr[i] = this->myArray[i];
        //tempArr[i] = new T(*this->myArray[i]);
    }
    for (int i = 0; i < this->elements; i  )
    {
        delete this->myArray[i];
    }
    delete this->myArray;
    this->myArray = tempArr;
    init(this->elements);
}

template <typename T>
void dynamicArray<T>::add(T dane)
{
    if (this->size == this->elements)
        this->expand();

    this->myArray[this->elements] = dane;
    this->elements  ;
}

int main()
{
    dynamicArray<obj*>* arr = new dynamicArray<obj*>();
    obj* so = new obj;
    so->fInt = 2;
    so->fFloat = 2;
    arr->add(so);
    obj* so2 = new obj;
    so2->fInt = 3;
    so2->fFloat = 3;
    arr->add(so2);
    so = arr->get(0);
    so2 = arr->get(1);
    std::cout << so->fInt << std::endl;
    std::cout << so->fInt;

}

In this for loop I would like to assign to temporary array elements of myArray but they are not the copies

    for (int i = 0; i < this->elements; i  )
    {
        tempArr[i] = this->myArray[i];
        //tempArr[i] = new T(*this->myArray[i]);
    }

and when I delete them they disappear from tempArr too.

    for (int i = 0; i < this->elements; i  )
    {
        delete this->myArray[i];
    }

I tried couple things but I can't find the solution.

tempArr[i] = new T(*this->myArray[i]);

I am not sure if this is the right track, but it's giving me a

'initializing': cannot convert from 'obj' to 'T'

and

'=' cannot convert from 'T*' to 'T'

CodePudding user response：

You got yourself confused, you have a pointer to an array of T, not a pointer to an array of T*, but some of your code is written as if you had the latter.

This (in expand)

for (int i = 0; i < this->elements; i  )
{
    delete this->myArray[i];
}
delete this->myArray;

should simply be

delete[] this->myArray;

You can't delete individual array elements because they are not (necessarily) pointers. And delete[] this->myArray; will invoke the destructor for all elements in your array.

And init can simply be deleted, because again it assumes that your array elements are pointers.

Try writing some code with dynamicArray<int>, so that your T is definitely not a pointer. That will find all the places where you've incorrectly assumed that T is a pointer (in case I've missed any).